FILED
                                                                United States Court of Appeals
                                     PUBLISH                            Tenth Circuit

                      UNITED STATES COURT OF APPEALS                    July 14, 2015

                                                                    Elisabeth A. Shumaker
                                TENTH CIRCUIT                           Clerk of Court
                       __________________________________


 PREDATOR INTERNATIONAL, INC., a
 Colorado corporation,

        Plaintiff,

 v.

 GAMO OUTDOOR USA, INC., a Florida
 corporation,                                             No. 14-1354

      Defendant.
 _________________________

 JOHN M. COGSWELL,

       Attorney – Appellant.



           APPEAL FROM THE UNITED STATES DISTRICT COURT
                   FOR THE DISTRICT OF COLORADO
                    (D.C. No. 1:09-CV-00970-PAB-KMT)


Submitted on the briefs:

John M. Cogswell, Cogswell Law Offices, P.C., Buena Vista, Colorado, for Attorney –
Appellant.


Before HARTZ, GORSUCH, and MORITZ, Circuit Judges.
HARTZ, Circuit Judge.
    Attorney John Cogswell appeals the imposition of a Rule 11 sanction. Acting on

behalf of Predator International, Inc., Cogswell filed a lawsuit in April 2009 in the United

States District Court for the District of Colorado against Gamo Outdoor USA, Inc. and

Industrias El Gamo, S.A. (collectively, Gamo). The original complaint alleged patent

infringement and other claims. When it appeared that Lee Phillips, a coinventor of the

patent at issue, was asserting that he still owned half the patent, Cogswell moved to

dismiss the infringement claim, explaining that Predator would litigate ownership in state

court with the expectation of reviving the patent-infringement claim once it had

established its ownership. The state litigation expanded after Gamo purchased Phillips’s

interest in the patent. Cogswell then moved in federal court to supplement Predator’s

complaint with a challenge to Gamo’s claimed interest in the patent and moved to amend

the complaint by reviving the patent-infringement claim. The district court denied the

motion.

       Eventually the district court imposed a Rule 11 sanction on Cogswell for filing the

motion to supplement and amend Predator’s complaint. It justified the sanction on the

grounds that he was forum shopping on the claims he wished to add, his motion came too

long after he had learned of Gamo’s purchase of Phillips’s interest in the patent, and

nothing had changed to justify his reinstating the patent-infringement claim. Cogswell

appeals the sanction. Exercising jurisdiction under 28 U.S.C. § 1291, we reverse. The

motion to supplement and amend was not unwarranted under existing law.

                                             2
       We address our jurisdiction, the requirements for a Rule 11 sanction, and the

application of these requirements to this case.

I.     DISCUSSION

       A.     Jurisdiction

       Because this case involves a patent, our jurisdiction could be questioned. For

actions filed before September 16, 2011, the United States Court of Appeals for the

Federal Circuit had exclusive jurisdiction over appeals from district-court decisions if the

lower court’s jurisdiction rested in whole or in part on 28 U.S.C. § 1338(a), which gives

district courts jurisdiction over civil actions arising under patent legislation. See

28 U.S.C. § 1295(a)(1) (2006).1 Section 1295(a)(1) might seem to deprive this court of

jurisdiction because a claim for patent infringement was included in Predator’s original

complaint, as well as in Predator’s first, second, and third amended complaints, filed

between May 2009 and March 2010. But at the time of Cogswell’s notice of appeal, the

most recent complaint was Predator’s fourth amended complaint, filed in September

2010, which did not contain a patent-infringement claim. And it is that complaint which

governs our jurisdiction.




1
 As a result of the Leahy-Smith America Invents Act (AIA), Pub. L. No. 112-29,
§ 19(b), 125 Stat. 284, 331–32 (2011), the Federal Circuit’s jurisdiction has been
changed. But the AIA applies only to civil actions commenced on or after September 16,
2011. See AIA § 19(e), 125 Stat. at 333; Wawrzynski v. H.J. Heinz Co., 

,
1378 (Fed. Cir. 2013).

                                              3
       This conclusion follows from two propositions. First, an amended pleading

“supersedes the pleading it modifies and remains in effect throughout the action unless it

subsequently is modified.” Gilles v. United States, 

, 1389 (10th Cir. 1990)

(en banc); see Mink v. Suthers, 

, 1254 (10th Cir. 2007) (“an amended

complaint super[s]edes an original complaint and renders the original complaint without

legal effect” (internal quotation marks omitted)). Second, a court’s subject-matter

jurisdiction ordinarily is determined by the situation at the time that jurisdiction is

invoked. This is true of federal district courts. See Grupo Dataflux v. Atlas Global Grp.,

L.P., 

, 570 (2004) (“the jurisdiction of the court depends upon the state of

things at the time of the action brought”) (internal quotation marks omitted)); cf. 

(noting exception to time-of-filing rule when lack of diversity jurisdiction is cured by

dismissal of a party); 16 James Wm. Moore et al., Moore’s Federal Practice

§ 107.41[2][c] (3d. ed. 2011) (“Removability is ordinarily determined as of the date the

notice of removal is filed.”). And it is also true of a federal appellate court, whose

jurisdiction is invoked by a notice of appeal. Thus, the Federal Circuit has held that it

lacked jurisdiction over an appeal because the patent claim originally brought in the

district court had been voluntarily dismissed without prejudice before entry of final

judgment and filing of the notice of appeal. See Gronholz v. Sears, Roebuck & Co.,

, 518 (Fed. Cir. 1987); see also Holmes Grp., Inc. v. Vornado Air

Circulation Sys., Inc., 

, 835 (2002) (Stevens, J., concurring in part and in the

judgment) (“[I]f the only patent count in a multicount complaint was voluntarily
                                               4
dismissed in advance of trial, it would seem . . . clear that the appeal should be taken to

the appropriate regional court of appeals rather than to the Federal Circuit.”); 

(Ginsburg, J., concurring in the judgment) (Because “no patent claim was actually

adjudicated” in district court, Federal Circuit lacked appellate jurisdiction.).

       Here the notice of appeal was filed after the fourth amended complaint was filed.

Later events—such as dismissal of a federal claim or mootness—can affect a court’s

jurisdiction. See Rockwell Int’l Corp. v. United States, 

, 473‒74 (2007)

(“[W]hen a plaintiff files a complaint in federal court and then voluntarily amends the

complaint, courts look to the amended complaint to determine jurisdiction.”); Winsness v.

Yocom, 

, 736 (10th Cir. 2006) (“Even if we assume that a credible threat of

prosecution existed before this lawsuit was filed, the prosecutors’ [post-complaint]

affidavits [disavowing an intention to prosecute] have rendered the controversy moot.”).

But no such events after the notice of appeal have been presented to us.2 We have

jurisdiction under 28 U.S.C. § 1291 and can proceed to the merits.



2
  We note that in response to Predator’s fourth amended complaint, Gamo pleaded a
counterclaim requesting a declaratory judgment that it had not infringed Predator’s
patent, and that pleading was operative at the time of the notice of appeal. Such a
counterclaim might now be sufficient to confer exclusive jurisdiction on the Federal
Circuit because under the AIA that exclusive jurisdiction now includes “an appeal from a
final decision of a district court . . . in any civil action arising under, or in any civil action
in which a party has asserted a compulsory counterclaim arising under, any Act of
Congress relating to patents . . . .” 28 U.S.C. § 1295(a)(1) (2012) (emphasis added); see
AIA, § 19(b), 125 Stat. at 331–32. But before the AIA, the Federal Circuit’s jurisdiction
depended on a claim “arising under” patent legislation. And “a counterclaim . . . cannot
                                                                                   Continued . . .
                                                5
       B.     The Rule 11 Standard

       Federal Rule of Civil Procedure 11 warns attorneys that by “presenting to the

court a pleading, written motion, or other paper,” they certify to the best of their

“knowledge, information, and belief, formed after an inquiry reasonable under the

circumstances,” that the paper meets the following conditions:

       (1) it is not being presented for any improper purpose, such as to harass,
       cause unnecessary delay, or needlessly increase the cost of litigation;
       (2) the claims, defenses, and other legal contentions are warranted by
       existing law or by a nonfrivolous argument for extending, modifying, or
       reversing existing law or for establishing new law;
       (3) the factual contentions have evidentiary support or, if specifically so
       identified, will likely have evidentiary support after a reasonable
       opportunity for further investigation or discovery; and
       (4) the denials of factual contentions are warranted on the evidence or, if
       specifically so identified, are reasonably based on belief or a lack of
       information.

Fed. R. Civ. P. 11(b). In short, Rule 11 requires that a “pleading be, to the best of the

signer’s knowledge, well grounded in fact, warranted by existing law or a good faith

argument for the extension, modification, or reversal of existing law, and . . . not

interposed for any improper purpose.” Coffey v. Healthtrust, Inc., 

, 1104

(10th Cir. 1993). “If, after notice and a reasonable opportunity to respond, the court

determines that Rule 11(b) has been violated, the court may impose an appropriate




serve as the basis for ‘arising under’ jurisdiction.” 

. Gamo’s
patent-related counterclaim does not defeat our jurisdiction.


                                              6
sanction,” meaning one “limited to what suffices to deter repetition of the conduct or

comparable conduct by others similarly situated.” Fed. R. Civ. P. 11(c)(1), (4).

       The district court imposed a Rule 11 sanction against Cogswell, Predator’s

attorney, for filing a motion to supplement its complaint with a challenge to Gamo’s

claimed interest in the patent and to amend its complaint by reviving the patent-

infringement claim. Because the court found “no evidence that Predator acted with

malice or bad faith,” Predator Int’l, Inc. v. Gamo Outdoor USA, Inc.,

No. 09-cv-00970-PAB-KMT, 

, at *8 (D. Colo. Jan. 17, 2014), the

question before us is whether the motion to supplement and amend the complaint was

unwarranted under the facts or law. To answer that question, the district court must

evaluate Cogswell’s conduct under a standard of “objective reasonableness—whether a

reasonable attorney admitted to practice before the district court would file such a

document.” Adamson v. Bowen, 

, 673 (10th Cir. 1988). Because our

adversary system expects lawyers to zealously represent their clients, this standard is a

tough one to satisfy; an attorney can be rather aggressive and still be reasonable. Even if

a legal position in a pleading is clearly contrary to current law, it is not sanctionable if the

position is warranted “by a nonfrivolous argument for extending, modifying, or reversing

existing law or for establishing new law.” Fed. R. Civ. P. 11(b)(2). This standard can be

compared to the lesser standard for sanctions under Rule 37(a)(5)(A) (for improperly

opposing discovery disclosure), which ordinarily must be imposed to compensate the

opposing party for its expenses unless the objection to disclosure “was substantially
                                               7
justified.” And even if counsel obnoxiously tries a court’s patience with unfounded or

silly arguments, the sanction must be based solely on those violations of Rule 11, not on

other rejected arguments that were in fact objectively warranted.

       On appeal we “apply an abuse-of-discretion standard in reviewing all aspects of a

district court’s Rule 11 determination. A district court would necessarily abuse its

discretion if it based its ruling on an erroneous view of the law or on a clearly erroneous

assessment of the evidence.” Cooter & Gell v. Hartmarx Corp., 

, 405

(1990). To evaluate the district court’s imposition of the sanction against Cogswell, we

set forth the chronology of relevant events, noting the applicable law as appropriate.

       C.     Application to This Case

       In January 2000, air-gun enthusiasts Tom May and Lee Phillips filed a provisional

patent application for a new type of air-gun pellet they had invented. A few months later,

Predator was formed to manufacture, promote, and sell the new pellet, with May as

President and Phillips as Vice President and Secretary. But Phillips was involved in an

automobile accident that led to a lengthy prison term, and he resigned from Predator in

early 2002, selling May “all of [his] capital stock and rights and interests in Predator

International, Inc.” Aplt. App. at 78. The patent application was granted in 2003. On

January 1, 2007, the current owners of Predator bought May’s interest in the company.

       About two years later, Predator discovered that Gamo was marketing an air-gun

pellet substantially identical to its own pellet, using virtually the same trade dress, slogan,

and advertising copy, which had allegedly caused customer confusion and damaged
                                               8
Predator’s reputation. May assigned his interest in the patent to Predator, and in April

2009, Cogswell filed on behalf of Predator a federal complaint against Gamo asserting

claims for trade-dress infringement, slogan infringement, copyright infringement,

violation of Colorado’s Consumer Protection Act, unjust enrichment, unfair competition,

and patent infringement.

       In February 2010 Predator attempted to obtain from Phillips a written assignment

of his patent-ownership rights. Phillips refused and claimed a 50% ownership interest in

the patent. His claim of ownership presented a problem for Predator’s patent-

infringement claim because a co-owner of a patent does not have standing to sue for

infringement unless all other co-owners join the suit. See Israel Bio-Eng’g Project v.

Amgen, Inc., 

, 1264–65 (Fed. Cir. 2007). The problem did not, however,

require dismissal of Predator’s patent-infringement claim. See Kunkel v. Topmaster Int’l,

Inc., 

, 695 (Fed. Cir. 1990) (“merely because a question of contract law

must be decided prior to reaching the infringement question does not defeat federal

subject matter jurisdiction” (internal quotation marks omitted)). Although the

infringement claim could not be decided before the ownership issue was resolved, the

federal court could assume supplemental jurisdiction over the patent-ownership claim,

see 28 U.S.C. § 1367(a) (district courts have supplemental jurisdiction “over all other

claims that are so related to claims in the action within [the court’s] original jurisdiction

that they form part of the same case or controversy”); Energy Recovery, Inc. v. Hauge,

, 820 (E.D. Va. 2000) (“precisely because patent ownership
                                              9
represents a necessary predicate issue, it is sufficiently related to Plaintiff’s patent non-

infringement claim to afford Plaintiff a basis for supplemental jurisdiction”); cf. 

n.1 (under former version of 28 U.S.C. § 1367, district court in patent

case would have pendent jurisdiction over claim of breach of patent-license contract). Or

the infringement proceedings could be stayed while ownership was litigated in state

court. See Loral Fairchild Corp. v. Matsushita Elec. Indus. Co., 

,

215‒18 (E.D.N.Y. 1994) (supplemental jurisdiction exercised over patent-ownership

claims in patent-infringement suit, but case stayed pending outcome in state court).

       But Predator took another course. On March 4, 2010, it moved to dismiss without

prejudice its patent-infringement claim, stating its intent to prove its exclusive ownership

in state court and then refile the claim in the federal lawsuit. Its motion to dismiss

explained:

       Predator vehemently disagrees that Mr. Phillips has any [patent] rights . . .
       and that he is, in fact, obligated to provide Predator with a written
       assignment evidencing that ownership. Nonetheless, in recognition of the
       fact that standing is a threshold issue in every action, Predator recognizes
       that it must resolve this ownership dispute with Mr. Phillips, obtain a
       formal patent assignment from him, or re-file with Mr. Phillips as a co-
       plaintiff, to cure the potential defect in standing. Rather than bring
       Mr. Phillips into this case and plead ancillary state law claims regarding
       ownership, resulting in a time-consuming and complicated sideshow over
       only one of multiple claims made in this case, Predator plans to proceed
       with litigation in Colorado state court against Mr. Phillips. Predator
       certainly hopes that this ownership dispute can be resolved swiftly so that it
       may re-file its patent infringement claim as soon as possible.

Predator, 

, at *1 (internal quotation marks omitted) (emphasis added).


                                              10
       In May, while its motion to dismiss was still pending, Predator moved to file a

fourth amended complaint excluding the patent-infringement claim. On September 9 the

federal district court granted the motion, and it later denied as moot Predator’s motion to

dismiss its infringement claim.

       The May motion to amend stated that “Predator seeks to voluntarily dismiss its

patent infringement claims . . . because it has discovered that it cannot prove that it had

standing to pursue these claims without a written assignment from Mr. Lee Phillips.” 

(emphasis added) (internal quotation marks omitted). Both Gamo and the district

court interpreted this statement as a concession that Predator lacked standing to bring the

claim. See 

*5. But Predator has always insisted that it owned the patent. It was

simply acknowledging that its ownership of the patent had to be litigated and expressing

its view that the best forum for that litigation would be the state court. That is quite

different from an admission that it lacked standing. Indeed, at the outset of a case it is

enough to allege the facts (here, ownership of the patent) establishing standing. If the

allegations are, as here, challenged, then the facts have to be litigated; but they can be

litigated in the forum where jurisdiction is at issue. The Supreme Court has taught:

“[E]ach element [of standing] must be supported in the same way as any other matter on

which the plaintiff bears the burden of proof, i.e., with the manner and degree of evidence

required at the successive stages of litigation.” Lujan v. Defenders of Wildlife, 

, 561 (1992). General allegations suffice at the pleading stage, although affidavits

may be necessary on a summary-judgment motion and ultimately a trial may be
                                              11
necessary to resolve the issue. See 

that a trial would be

necessary but wanted that trial to be in state court. As Predator later stated in its response

to Gamo’s motion for sanctions:

       Predator has never conceded that it did not have standing. It has only
       conceded that, in light of GAMO’s objection to Predator’s full ownership
       of the patent, a hearing or trial on standing would be required and Predator
       believed it would be more sensible to deal with it in state court than in this
       Court. . . .

Predator, 

, at *5 (brackets and internal quotation marks omitted).

       There has been no contention that Predator’s claim of ownership was frivolous.

According to Predator’s pleadings, not only had Phillips sold to May “all of [his] capital

stock and rights and interests in Predator International, Inc.,” Aplt. App. at 78, but

Phillips had never requested or received royalties, objected to Predator’s holding itself

out as the sole owner of the patent, or attempted to make use of the patent. Predator

further alleged that the patent had always been treated as an asset on its books, that May

believed (and Predator’s investors and subsequent owners relied on that belief) that

Phillips had no remaining patent-ownership interest, and that in 2003 Phillips had

confirmed to May that he had no interest in the patent.

       Meanwhile, in April 2010 Predator had filed suit against Phillips in Colorado state

court. Its complaint sought a determination that Phillips had transferred or must transfer

his interest in the patent to May (and consequently to Predator). It presented six legal

theories supporting that relief: (1) breach of contract, (2) breach of the implied duty of

good faith and fair dealing, (3) contract reformation, (4) breach of implied contract,
                                             12
(5) breach of implied exclusive license, and (6) breach of fiduciary duty, all centered on

the same allegations of Phillips’s refusal to acknowledge Predator as the exclusive owner

of the patent.

       In June, Phillips assigned his purported interest in the patent to Gamo. Predator

learned about the assignment no later than September 27, and on November 2 it filed in

state court an amended complaint adding new claims against Phillips that his assignment

to Gamo breached his duties to Predator and that Predator still owned the patent. Soon

after, Gamo moved to intervene in the state-court suit, and the suit expanded further.

Alleging that he had never relinquished his rights to Predator or the patent, Phillips filed

on November 15 eight counterclaims against Predator, asserting that (1) Predator had

breached its fiduciary duty to him as a 50% stockholder; Predator had (2) stolen and

(3) converted his rights in the company; (4) Predator had been unjustly enriched at his

expense; (5) Predator owed him an accounting; and (6–8) Phillips’s sale and assignment

to May was void and Phillips retained a 50% ownership interest in Predator. The next

day Phillips filed a third-party complaint against Tom May. He asserted claims for

(1) breach of fiduciary duty, (2) civil theft, (3) conversion, (4) unjust enrichment,

(5) fraudulent misrepresentation, (6) constructive fraud, and (7) an accounting; and he

sought a declaratory judgment that (8) Phillips’s assignment to May was void, (9) Phillips

owned 50% of Predator, (10) May’s sale of Predator to its current owners was void, and

(11) Phillips retained a 50% interest in the patent. Also on that day Gamo submitted a

proposed answer and six counterclaims against Predator (subject to Gamo’s being
                                             13
permitted to intervene). The counterclaims sought damages for (1) fraudulent

misrepresentation and (2) fraudulent concealment, based on Predator’s allegedly false

allegations in its original federal-court complaint that it had full ownership of the patent

(and therefore standing to claim infringement), which induced Gamo to expend resources

defending against those allegations. The counterclaims further requested a declaratory

judgment that (3) Phillips’s sale of his patent interest to Gamo was valid, (4–5) Gamo

now owned 50% of the patent, and (6) Predator lacked standing to pursue a patent-

infringement claim in federal court.

       In December Predator moved for a separate trial on patent ownership. On

January 1, 2011 (yes, the state court worked that day) the court granted Gamo’s motion to

intervene and denied the motion for separate trials. Later in January, Predator filed

motions to dismiss Gamo’s counterclaims (except for patent ownership) on the grounds

of standing and state-federal comity and to dismiss Phillips’s counterclaims on the

grounds that Phillips’s sale and assignment to May was valid and that his claims were

barred by the statute of limitations or laches. On April 1 the state court denied the

motions, save for dismissing Gamo’s counterclaim that Predator lacked standing in

federal court. It also awarded Gamo some attorney fees because Predator’s motion to

dismiss two of the counterclaims failed to cite any legal authority.

       Three months later, on July 11, 2011, Predator filed in federal court the motion

that is the source of the Rule 11 sanction. It moved (1) for leave to file a supplemental


                                             14
complaint asserting, among other things, a patent-ownership claim against Gamo,3 and

(2) for leave to amend its complaint to reassert its patent-infringement claim, although

requesting a stay of the trial of the infringement claim until Predator first proved its full

ownership of the patent.

       Neither request was unwarranted under the facts or the law. The rule governing

motions to supplement states that “the court may, on just terms, permit a party to serve a

supplemental pleading setting out any transaction, occurrence, or event that happened

after the date of the pleading to be supplemented.” Fed. R. Civ. P. 15(d). Leave to

supplement a complaint with “post-complaint transactions, occurrences or events . . .

should be liberally granted unless good reason exists for denying leave, such as prejudice

to the defendants.” Walker v. United Parcel Serv., Inc., 

, 1278 (10th Cir.

2001) (internal quotation marks omitted). Similarly, for motions to amend, “[t]he court

should freely give leave when justice so requires.” Fed. R. Civ. P. 15(a)(2); see Minter v.

Prime Equip. Co., 

, 1208 (10th Cir. 2006) (“in general permission is

liberally granted where there is no prejudice” (internal quotation marks omitted)); Hardin

v. Manitowoc-Forsythe Corp., 

, 456 (10th Cir. 1982) (“Rule 15 was

promulgated to provide the maximum opportunity for each claim to be decided on its

merits rather than on procedural niceties.”).

3
  The motion to supplement included claims in addition to the patent-ownership claim
against Gamo. But we ignore these claims because the sanction imposed by the district
court was not based on Predator’s filing them.


                                                15
       On its face, Predator’s motion to supplement conformed to Rule 15(d). Predator

had no ownership dispute with Gamo until Gamo acquired Phillips’s interest in the

patent. The magistrate judge noted that it was undisputed that the supplemental claim

was “premised on ‘transactions, occurrences, or events that happened after the date of the

pleading to be supplemented.’” Predator Int’l, Inc. v. Gamo Outdoor USA, Inc.,

No. 09-cv-00970-PAB-KMT, 

, at *5 (D. Colo. Sept. 19, 2011)

(quoting Fed. R. Civ. P. 15(d) (brackets omitted)). Predator could have brought the

patent-ownership claim in a separate action and then moved to consolidate the actions.

Supplementation under Rule 15(d) is simply a more efficient vehicle to accomplish that

objective. See Arp v. United States, 

, 574 (10th Cir. 1957) (“Had the court

refused permission to file [the supplemental complaint], the Government could have

proceeded by an original complaint in an independent action, and the identical issues

would have been presented and determined. We find no abuse of discretion by the trial

court [in allowing supplementation under Rule 15(d) instead].”); see also 6A Charles A.

Wright et al., Federal Practice and Procedure § 1506 (3d ed. 2010) (“[T]he usual effect of

denying leave to file a supplemental pleading because it states a new cause of action is to

force [the] plaintiff to institute another action and move for consolidation under Rule

42(a) in order to litigate both claims in the same suit, a wasteful and inefficient result.”

(footnote and internal quotation marks omitted)). (In response to Gamo’s motion for

sanctions, Predator argued: “By proposing [the patent-ownership claim] under

Fed.R.Civ.P. . . . 15(d) . . . , Predator was seeking permission, in the discretion of the
                                              16
Court, to have these claims heard in this case and not in a separate proceeding in

furtherance of the policy of conservation of judicial resources.” Aplt. App. at 167.)

       Likewise, Predator’s request to amend the complaint by reinstating the patent-

infringement claim was proper on its face. It was accompanied by a request to stay

proceedings on the claim until resolution of Predator’s claim that it had sole ownership of

the patent. Thus, the burden on the federal court was essentially the same as that

anticipated when Predator was permitted to delete the infringement claim from its

complaint on the understanding that it intended to refile and pursue the claim once

ownership of the patent was resolved. And there was no problem in reasserting the claim

without conclusive evidence of standing. As previously noted, Predator did not concede

a lack of standing. It alleged the factual basis for standing and conceded only that

standing would have to be proved. That is sufficient for the pleading stage. See 

.

       Nevertheless, the motions to supplement and amend could be denied if there was

good reason for denial. And if the grounds for denial were so strong and obvious that the

motions were unwarranted, then the Rule 11 sanction was proper. In our view, however,

the district court stated inadequate reasons for deciding that the motions were

unwarranted.

       The district court gave three reasons for the sanction. First, the court held that

Predator’s motion was sanctionable “forum shopping.” Predator, 

, at

*6; see 

Second, the court held that there was no justification for delaying the
                                             17
motion until July 2011, long after the deadline for amending pleadings and at least ten

months after Predator learned of Phillips’s assignment to Gamo of his interest in the

patent. See 

Third, the court noted that Predator had no better ground for

asserting standing than it had when it dismissed the patent-infringement claim. Although

acknowledging Predator’s argument that “it never conceded its lack of standing, only its

lack of evidence of standing,” the court viewed this as “a distinction without a

difference.” 

on Predator’s statement in its response to the motion for

sanctions that “Predator, . . . concerned that [Phillips’s] Sale and Assignment [to May of

his interest in Predator] was not by itself sufficient to show standing, [had been]

compelled by professional prudence [in the spring of 2010] to dismiss its patent

infringement claim without prejudice,” Aplt. App. at 148, the court said that “[t]o reassert

an identical claim without having obtained additional evidence of standing was therefore,

by Predator’s own assessment, imprudent,” Predator, 

, at *5. We

discuss each of these three grounds.

              1.     Forum Shopping

       The first reason given by the district court for sanctioning Cogswell was that

Predator’s motion was illegitimate forum shopping. It said:

       Forum shopping may constitute an improper purpose under Rule 11 where
       a party attempts to avail itself of a forum it perceives to be more favorable
       without any legal or factual basis for doing so, thereby causing unnecessary
       delay, or needlessly increasing the cost of litigation. See Bolivar v.
       Pocklington, 

, 32 (1st Cir. 1992); Fransen v. Terps Ltd.
       Liability Co., 

, 660 (D. Colo. 1994); Cusano v. Klein, 

, at *4 (C.D. Cal. Jan. 29, 2007).
                                             18


(brackets and internal quotation marks omitted).

       There was no forum shopping with respect to the infringement claim, which had

not been (and could not have been) brought in state court, see 28 U.S.C. § 1338(a) (state

courts do not have jurisdiction over patent-infringement claims), contrary to the district

court’s erroneous statement that Predator had “voluntarily dismiss[ed] that claim and

refil[ed] it in state court,” Predator, 

, at *1 (citation omitted). But even

with respect to the patent-ownership claim, the court misconceived the pertinent legal

doctrine on forum shopping. “Forum shopping is not an improper purpose [under Rule

11] if a ground for federal jurisdiction arguably exists.” 2 James Wm. Moore et 

, at § 11.11[8][b]. There is no impropriety simply in pursuing the same claim

simultaneously in state and federal courts. The general rule is that “both the state court

and the federal court, having concurrent jurisdiction, may proceed with the litigation at

least until judgment is obtained in one of them which may be set up as res judicata in the

other,” Donovan v. City of Dallas, 

, 412 (1964) (internal quotation marks

omitted), and even then, it is ordinarily the latter court that must decide the question of

res judicata, see 

court distinguished Donovan because the holding in that

case was that the state court could not enjoin a federal lawsuit raising a claim similar to

one disposed of in the state court. But the Supreme Court’s dictum in Donovan is clear

and states well-settled law. See United States v. Lot 85, Cnty. Ridge, 

, 742

(10th Cir. 1996); Aluminum Prods. Distribs., Inc. v. Aaacon Auto Transp., Inc., 

1381, 1383–84 (10th Cir. 1977); see also Colo. River Water Conservation Dist. v. United

States, 

, 817 (1976) (“Generally, as between state and federal courts, the rule

is that the pendency of an action in the state court is no bar to proceedings concerning the

same matter in the Federal court having jurisdiction.” (internal quotation marks omitted)).

       The three opinions cited by the district court in support of its above-quoted

statement on forum shopping do not support the sanction here. In 

–32, a Rule 11 sanction was imposed on the sole shareholder of certain corporations

who, after dismissal of claims against the defendant by the corporations, brought the

same claim in his own name against the same defendant before another judge (of the

same court). The claims clearly belonged to the corporations, not the shareholder. Here,

the claims to be added by Predator’s motion were legally sound. In 

–60, the court imposed Rule 11 sanctions because the plaintiff filed a suit that was

clearly meritless because of the res judicata effect of a prior state-court judgment. Here,

there was no state-court judgment when Predator filed its motion. And in Cusano, 

, at *4, the district court simply ordered an attorney to show cause why he

should not be sanctioned for filing a frivolous motion to recuse the judge. In each of the

three cases the sanctioned attorney was trying to proceed before another court or another

judge of the same court. The basis of the sanction, however, was not forum shopping

simpliciter but, rather, filing a pleading that was patently unfounded. There has been no

such challenge to the legal or factual basis of Plaintiff’s additional claims, nor to the

district court’s jurisdiction to hear them.
                                              20
       This is not to say that a federal court must always permit amendment of a

complaint to add a claim already pending in state court. The Supreme Court has

recognized several abstention doctrines, under which a federal court should not hear a

case when the same claims are before a state court. But the district court did not mention

any of these doctrines, and we would be loath to affirm a Rule 11 sanction because of a

legal doctrine that was not invoked by the court that imposed the sanction. We suspect

that a district court would not think it appropriate to say in that circumstance that any

“reasonable attorney admitted to practice before the district court,” 

, would have known of the doctrine precluding the pleading filed by the attorney.

       Moreover, we cannot say that any abstention doctrine made Cogswell’s action

unreasonable. Some certainly would not justify abstention here. And to the extent that

others could justify abstention, they are discretionary, and their application by the district

court was not so predictable in this case that to pursue the motion to supplement and

amend was legally unwarranted.

       The three more traditional abstention doctrines—which apply to cases (1)

“presenting a federal constitutional issue which might be mooted or presented in a

different posture by a state court determination of pertinent state law,” Colorado 

(internal quotation marks omitted); (2) “where there have been presented

difficult questions of state law bearing on policy problems of substantial public import

whose importance transcends the result in the case then at bar,” id.; or (3) where “federal

jurisdiction has been invoked for the purpose of restraining state criminal
                                              21
proceedings, . . . state nuisance proceedings[,] . . . or collection of state taxes,” 

817—are irrelevant here.

       More relevant is the Colorado River doctrine, although it is “considerably more

limited,” 

than the previously mentioned “extraordinary and narrow” traditional

abstention doctrines, 

Under the Colorado River doctrine, “reasons of wise

judicial administration” may require dismissal in favor of concurrent state proceedings.

As the Supreme Court later explained, Colorado River recognized four factors

to consider when deciding whether to abstain from exercising jurisdiction: (1) in an in

rem action, whether the federal court was the first to assume jurisdiction over the

property; (2) “the inconvenience of the federal forum”; (3) “the desirability of avoiding

piecemeal litigation”; and (4) “the order in which jurisdiction was obtained by the

concurrent forums.” Moses H. Cone Mem’l Hosp. v. Mercury Constr. Corp., 

,

15 (1983). These four factors do not support abstention here: this is not an in rem action,

the federal forum was not inconvenient, exclusive federal jurisdiction over patent-

infringement claims would necessarily result in some degree of piecemeal litigation, and

the federal forum had jurisdiction first. Moses H. Cone, however, identified other factors

that may be more applicable, “such as the vexatious or reactive nature of either the

federal or the state action . . . ; whether federal law provides the rule of decision . . . ; and

the adequacy of the state court action to protect the federal plaintiff’s rights . . . .” Fox v.

Maulding, 

, 1082 (10th Cir. 1994) (citing Moses H. 

n.20, 23, 28). And “[o]ther courts also have considered whether the party opposing
                                               22
abstention has engaged in impermissible forum-shopping.” 

“[n]o single

factor is dispositive” and “[o]nly the clearest of justifications will warrant dismissal.” 

marks omitted); see FDIC v. Nichols, 

, 637 (9th Cir.

1989) (“We are aware of no doctrine of abstention or deference of jurisdiction which

authorizes federal courts to decline to exercise jurisdiction on [forum-shopping]

ground[s] alone.”).

       Also relevant is the discretion of the district court to refuse to exercise jurisdiction

over a declaratory-judgment claim. See Wilton v. Seven Falls Co., 

, 286‒87

(1995) (noting that the Declaratory Judgment Act, 28 U.S.C. § 2201(a), “provides that a

court ‘may declare the rights and other legal relations of any interested party seeking such

declaration’”). District courts should consider five factors:

       [1] whether a declaratory action would settle the controversy; [2] whether it
       would serve a useful purpose in clarifying the legal relations at issue;
       [3] whether the declaratory remedy is being used merely for the purpose of
       procedural fencing or to provide an arena for a race to res judicata;
       [4] whether use of a declaratory action would increase friction between our
       federal and state courts and improperly encroach upon state jurisdiction;
       and [5] whether there is an alternative remedy which is better or more
       effective.

Mid-Continent Cas. Co. v. Vill. at Deer Creek Homeowners Ass’n, 

, 980–81

(10th Cir. 2012) (internal quotation marks omitted). Ultimately, however, the issue for

the court to decide is simply “whether the controversy can better be settled in a pending

action.” ARW Exploration Corp. v. Aguirre, 

, 454 (10th Cir. 1991). This is

a “practical” decision, St. Paul Fire & Marine Ins. Co. v. Runyan, 

, 1170

                                              23
(10th Cir. 1995), which may turn on any number of nuances, making anticipation of a

district court’s decision difficult, if not impossible, to predict.

       Under these authorities, Predator’s effort to pursue its patent-ownership claim in

federal court was, if not guaranteed to be successful, at least objectively reasonable. It

would not have been clear to a reasonable attorney that denial of the motion to amend

was demanded by settled law. Consider the full context. When Predator originally sued

Phillips in state court, it was suing a defendant who was not a party in the federal

proceedings and the subject matter of the suit—patent ownership—was distinct from the

issues raised in the federal litigation, with no significant overlapping law or facts. But

after Gamo bought Phillips’s interest in the patent, various counterclaims were filed in

state court that significantly expanded the issues. Predator moved to dismiss the new

counterclaims and sought to have the patent-ownership claim tried separately. The state

court rejected Predator’s requests (except for dismissing one counterclaim), thereby

reducing the efficiency in having the state court, rather than the federal court, decide the

ownership claim. Three months later, Predator moved to amend its federal complaint to

add an ownership claim to its other claims against Gamo. At that time the state court had

issued no rulings on the ownership claim—neither party had sought any—and little

discovery had been conducted. Moreover, bringing the ownership claim in federal court

had several advantages: it avoided delays in the federal infringement claim that could

result from appeals in state court of any decision regarding patent ownership; it

consolidated claims against a party already before the federal court; and it avoided
                                               24
piecemeal litigation (even if Predator proved its patent ownership in state court, it would

still need to file an infringement action in federal court because of exclusive federal

jurisdiction over patent claims under 28 U.S.C. § 1338). Predator adverted to these

considerations when it gave the district court the following reasons for filing its motion to

supplement and amend its complaint:

       to accelerate final judgment on the standing issue, to mitigate GAMO’s
       splitting of claims between this Court and state court, to provide a hedge
       against the error-ridden proceeding in state court which had the appearance
       of an interminable controversy replete with appeals, remands and retrials,
       and to permit this Court to determine standing which would have been the
       case if GAMO, pursuant to its duty of candor and Fed.R.Civ.P. 26, had
       disclosed to this Court and Predator in June 2010 that it had acquired
       Phillips’ interests, if any, in the patent.

Predator, 

, at *5 (internal quotation marks omitted). If in those

circumstances it was “unwarranted” for Predator to seek to pursue its ownership claim in

federal court, then it is hard to see how it could ever be proper to pursue in federal court a

state-law claim already pending in state court.

       It is no answer to say that Predator was unhappy with rulings by the state court,4

because we would presume that parties seeking federal-court review anticipate there

being an advantage to doing so. In any event, the state court had not issued any rulings

4
 After listing Predator’s state-court defeats, see Predator, 

, at *2, the
district court referred to those “adverse rulings” as motivating Predator’s filing of the
motion to amend and supplement, 

*6, without differentiating between those
rulings that occurred before the filing of the motion (the denial of the motions for
separate trials and to dismiss Phillips’s and Gamo’s counterclaims) and those that
occurred after it was filed (the denial of a motion to recuse the judge and the granting of a
motion to disqualify Cogswell).

                                             25
related to the merits of the claim Predator sought to pursue in federal court. The only

substantive rulings in state court before Predator filed its motion to supplement and

amend its complaint were the rulings that defeated the efficiencies of pursuing the

ownership claim in state court: the ones that made clear that the state-court action was

going to be significantly expanded and the patent-ownership claim would be tried with all

the other claims. (The sole other ruling was an award of $2,481.50 in attorney fees for

Predator’s unsupported motion to dismiss two of Gamo’s counterclaims.) It was only on

July 15, 2011, four days after the motion to supplement and amend was filed, that Gamo

and Phillips renewed a motion to disqualify Cogswell (two earlier attempts had been

unsuccessful), which was not granted until November 29, 2011.

       In holding that Predator’s motion to supplement and amend its complaint was not

unwarranted, we find support in a federal district-court decision on a similar matter in a

similar case. In Energy 

‒16, the parties disputed

whether the defendant had transferred to the plaintiff his rights to a patent. The plaintiff

initially sued the defendant in state court for tortious business interference,

misappropriation of trade secrets, detinue, and common-law and statutory conspiracy.

See 

The plaintiff then filed suit in federal court against the defendant, bringing

Lanham Act claims for unfair competition and cyber piracy and a request for a

declaration of patent noninfringement. See 

requested the federal court

to stay the noninfringement action because the ownership issue—a matter of state law—

would be resolved in the state litigation. The district court decided not to stay the action.
                                              26
First, the proceedings on the plaintiff’s other federal claims (like Predator’s) would

continue anyway. Second, the state court lacked jurisdiction over patent-infringement

claims, so it could not address all issues presented in the declaratory-judgment claim.

And third, prompt resolution of the patent-ownership issue in state court was not

guaranteed, and the lack of progress on the issue in state court meant that proceeding in

federal court would not interfere excessively with the state proceedings. All in all, the

court thought that proceeding with the claim would serve judicial economy. See 

       To recapitulate, Predator had not forum-shopped its patent-infringment claim

because, contrary to the district court’s understanding, it had not filed (and could not file)

the claim in state court. And as for the patent-ownership claim, the legal proposition

relied on by the district court—that a party engages in improper forum shopping if it

“attempts to avail itself of a forum it perceives to be more favorable without any legal or

factual basis for doing so,” Predator, 

, at *4 (emphasis added)—does

not apply because there was a legal and factual basis for pursuing the claim in federal

court even though it was already before the state court. Although there are legal

doctrines under which the district court could have abstained from considering the

ownership claim, the district court did not set forth the doctrines in its order; a fortiori,

the court made no finding that a reasonable attorney would have known that the motion

to amend would be precluded by one of those doctrines; and, in any event, none of those

doctrines clearly precluded the proposed amendment. As a result of its legal error, the
                                               27
district court abused its discretion in relying on forum shopping as a ground for imposing

the Rule 11 sanction.

       On this ground alone, we must reverse the award of sanctions and remand for

further proceedings. When a court bases its exercise of discretion on the confluence of

several factors and it was improper for the court to rely on one of those factors, we must

reverse “unless we can say as a matter of law that it would have been an abuse of

discretion for the trial court to rule otherwise.” Ashby v. McKenna, 

, 1151

(10th Cir. 2003) (internal quotation marks omitted). That standard for affirmance is not

satisfied here. The district court’s other two grounds for imposing sanctions are not

compelling, and at the least do not mandate the full sanction imposed. We briefly discuss

each ground.

               2.    Delay

       To support the sanctions imposed on Cogswell, the district court relied in part on

the delay between when Predator learned of Gamo’s acquisition of Phillips’s patent-

ownership rights and when it moved to supplement and amend its complaint in federal

court, see Predator, 

, at *5, particularly in light of the pretrial order’s

deadline for amending pleadings, which had expired nearly two years earlier.

       The deadline in the pretrial order, however, was the final date to “amend”

pleadings. 

And even if read to encompass motions to supplement the

complaint, but see Ohio Valley Envtl. Coal. v. U.S. Army Corps of Eng’rs, 

, 256 (S.D. W. Va. 2007) (deadline for amending pleadings did not apply to
                                            28
supplemental pleadings), it could not preclude Predator from filing a separate suit on the

ownership claim against Gamo, and then seeking consolidation of the two suits. The

district court could decide that the supplemental claim should proceed as a separate case;

but there was nothing unwarranted in giving the district court the choice of whether to

consolidate the claims with those that were pending. See Wright et 

, § 1506

(“[T]he usual effect of denying leave to file a supplemental pleading because it states a

new cause of action is to force [the] plaintiff to institute another action and move for

consolidation under Rule 42(a) in order to litigate both claims in the same suit, a wasteful

and inefficient result.” (footnote and internal quotation marks omitted)).

       As for the motion to amend to add the patent-infringement claim, it was

objectively reasonable for Predator to think that the amendment did nothing more than

follow up on what everyone had anticipated when the infringement claim was dropped

from Predator’s complaint. Indeed, when Gamo had argued that Predator’s dismissal of

its infringement claim should be conditioned on reimbursement of the expenses it had

incurred in defending the claim, the magistrate judge “agree[d] with Predator that much

of the work and discovery related to Predator’s patent infringement claim is . . .

applicable . . . to a later-filed patent infringement action, should Predator choose to

pursue it.” Predator Int’l, Inc. v. Gamo Outdoor USA, Inc., No. 09-cv-00970-PAB-

KMT, 

, at *8 (D. Colo. Sept. 9, 2010). If anything, the amendment

was premature, not late, because ownership of the patent had not yet been resolved. In


                                             29
these circumstances, it was not objectively unreasonable for Predator to pursue the

motion to supplement and amend despite the pretrial order’s deadline.

         Turning to the nine-month delay between when Predator learned that Gamo had

acquired Phillips’s interest in the patent and when Predator moved to add its claims in

federal court, Predator reasonably argued that the important date was not when Gamo

acquired Phillips’s interest, or even when Predator learned of the acquisition, but rather

when it became clear that the state-court litigation would not be a focused dispute

between Predator and Phillips regarding who owned the patent. It was not clear that the

state case had significantly expanded until (1) Gamo and Phillips sought to add numerous

claims in the state case, (2) the state court denied Predator’s motion to try the ownership

issue separately, and (3) the state court, over Predator’s objections, approved the

expansion of the case. Moreover, since it then became clear that Predator’s rival in the

state case would be Gamo, which was already the opposing party in the federal case,

there was less efficiency in segregating the ownership claim from those already in federal

court.

         The district court acknowledged Predator’s arguments regarding why it now made

sense to litigate ownership in federal court, but it did not address the contention that the

nature of the state litigation had significantly changed in April 2011, when the state court

confirmed that Gamo’s claims could be litigated in that forum. Rather, it relied on

“Predator’s assertion that, had it known of the assignment earlier, it would have

withdrawn its declaratory judgment claim from the state court and litigated it in this
                                              30
Court[, which] is difficult to square with its decision to continue litigating in state court

for at least ten months before taking any action in response to the assignment.” Predator,

, at *5. But the court omitted an important component of Predator’s

assertion. What Predator said was that if Gamo had informed Predator of the sale in

June, “while Predator’s patent infringement claim was still pending” in federal court,

Pl.’s Resp. to Defs.’ Mot. for Sanctions at 27, Predator Int’l, Inc. v. Gamo Outdoor USA,

Inc., No. 1:09-cv-00970-PAB-KMT (D. Colo. Jan. 12, 2012) (emphasis added), it would

have dismissed the state case and kept the infringement claim alive. Once the patent

claim had been dismissed, however, there would be stronger reasons to continue with the

state case, at least absent further complicating developments. We are not saying that the

district court abused its discretion in denying the motion to supplement and amend

because of Predator’s delay in bringing the motion. But in light of Predator’s asserted

justifications, the delay did not make it objectively unreasonable for Predator to seek to

add the claims.

              3.      Standing

       Finally, the district court held that Predator had no basis to reassert its patent-

infringement claim because it had no new evidence of standing. It stated that a lack of

standing and a lack of evidence of standing is “a distinction without a difference,”

Predator, 

, at *5; but as discussed above, Predator had no obligation to

prove standing conclusively at the pleading stage, see 

. And

whether or not it had been “[]prudent” for Predator to dismiss the claim in 2010,
                                              31
Predator, 

, at *5, later developments in the state-court litigation—such

as the threat of complicated and prolonged proceedings—could have reasonably led

Predator to reassess that determination. In particular, if Predator could not refile its

infringement claim until it had proved its ownership of the patent in state court, then the

longer the delay in state court (and the prospect of delay had increased as the state

litigation expanded), the greater the chance that the statute of limitations on the

infringement claim could reduce any recovery Predator might obtain against Gamo, a

point specifically argued to the district court by Predator. In short, Predator’s standing

was adequately supported by the allegations in the proposed amended complaint, and

there were proper grounds for it to change its mind and now seek to litigate ownership in

the federal court. Again, we do not suggest that denial of the motion to amend was an

abuse of discretion, but only that the motion to amend was not unwarranted.

       In light of our determination that the Rule 11 sanction must be reversed, we need

not address Cogswell’s other arguments for reversal, except to say that we reject the

unfounded contention that the district judge was biased.

II.    CONCLUSION

       We REVERSE the district court’s judgment imposing sanctions on Cogswell and

REMAND for further proceedings.




                                              32