RECOMMENDED FOR FULL-TEXT PUBLICATION
                                    Pursuant to Sixth Circuit Rule 206
                                           File Name: 07a0405p.06

                       UNITED STATES COURT OF APPEALS
                                       FOR THE SIXTH CIRCUIT
                                         _________________


                                                     X
                             Plaintiffs-Appellants, -
 JAMES I. PRATER et al.,
                                                      -
                                                      -
                                                      -
                                                          No. 06-4393
          v.
                                                      ,
                                                       >
 OHIO EDUCATION ASSOCIATION,                          -
                              Defendant-Appellee. -
                                                      -
                                                      -
                                                     N
                      Appeal from the United States District Court
                     for the Southern District of Ohio at Columbus.
                 No. 04-01077—Edmund A. Sargus, Jr., District Judge.
                                       Argued: September 13, 2007
                                  Decided and Filed: October 3, 2007
        Before: SUTTON and McKEAGUE, Circuit Judges; FORESTER, District Judge.*
                                           _________________
                                                 COUNSEL
ARGUED: David M. Cook, COOK, PORTUNE & LOGOTHETIS, Cincinnati, Ohio, for
Appellants. Rodger L. Eckelberry, BAKER & HOSTETLER, Columbus, Ohio, for Appellee.
ON BRIEF: David M. Cook, Robert E. Rickey, Stephen A. Simon, COOK, PORTUNE &
LOGOTHETIS, Cincinnati, Ohio, for Appellant. Rodger L. Eckelberry, Manuel Jose Asensio III,
BAKER & HOSTETLER, Columbus, Ohio, for Appellee. Michael F. Saggau, Daniel W. Sherrick,
ASSOCIATE GENERAL COUNSEL, Detroit, Michigan, Lisa M. Smith, Samuel C. McKnight,
KLIMIST, McKNIGHT, SALE, McCLOW & CANZANO, Southfield, Michigan, for Amici Curiae.
                                           _________________
                                               OPINION
                                           _________________
        SUTTON, Circuit Judge. James Prater and several other retired employees of the Ohio
Education Association (“OEA”) claim that OEA improperly terminated their health benefits, which
(they say) had become vested and irreducible through a series of collective bargaining agreements.
Relying in part on our decision in Maurer v. Joy Technologies, Inc., 

(6th Cir. 2000),
the district court rejected the claims as a matter of law. Because we conclude that Maurer does not

        *
          The Honorable Karl S. Forester, Senior District Judge for the Eastern District of Kentucky, sitting by
designation.


                                                       1
No. 06-4393           Prater et al. v. Ohio Education Association                            Page 2


apply here, because after-the-fact unilateral summary plan descriptions cannot supercede the
amendment provisions in a collective bargaining agreement and because the contracts are otherwise
ambiguous about whether they promise lifetime, irreducible health benefits to employees upon their
retirement, we reverse.
                                                 I.
        In its capacity as a union, OEA represents teaching professionals throughout Ohio. Unions
are employers too, however, and, in its capacity as an employer, OEA employs numerous individuals
who are represented by two other unions: the Professional Staff Union (“PSU”) and the Ohio
Associate Staff Union (“OASU”). OEA has negotiated several collective bargaining agreements
with these unions, and these agreements have provided for retiree healthcare benefits since 1978 for
PSU retirees and since 1981 for OASU retirees. Plaintiffs Montgomery and Whaley, former
associate staff employees of OEA, retired in 1999 and 2000, and they seek to represent a class of
OASU retirees. Plaintiffs Thorley, Prater and Westfall, former professional employees of OEA,
retired between 1984 and 1994, and they seek to represent a class of PSU retirees.
        The OASU Agreements. When Montgomery and Whaley retired, the collective bargaining
agreement for OASU employees said that it represented “the full and complete commitments
between both parties and [could] be altered . . . only through the voluntary, mutual consent of the
parties in a written and signed amendment.” JA 1101. The agreement provided active employees
with medical insurance covering “hospitalization; surgical; major-medical; out-patient X-ray; EKG;
laboratory; prescription drug; dental; and optical.” JA 1080. Retirees, the agreement said, “shall
be included in the Association group in regard to: hospitalization; surgical; out-patient; and major-
medical coverage,” but, “[a]fter the retiree reaches age 65, the Association is required to provide
only major-medical coverage.” JA 1086. The collective bargaining agreement also required the
company to give each employee “an individual contract guaranteeing the retiree health benefits at
the time of retirement.” 

Agreements. Like the OASU contract, the PSU collective bargaining agreements
in force when Prater, Thorley and Westfall retired provided that changes could be made “only by
an amendment properly signed and ratified by each party.” JA 1387, 1501, 1566. The first
provision for retiree benefits, in a subsection entitled “Continuation of Benefits,” said that “[t]he
Association shall continue to provide all benefits provided by Sections 11.0112 and 11.0113 of this
Contract for each retired employee to age sixty-five.” JA 1357 (Thorley); JA 1468 (Prater); see also
JA 1547–48 (Westfall). The next subsection, entitled “Reimbursement for Cost of Medicare,” said
that OEA “shall reimburse each retired employee over age sixty-five . . . for the cost of Medicare
Part B.” 

the next subsection, entitled “Supplement to Medicare,” the agreement said
that OEA “shall supplement the benefits of Medicare Parts A and B to provide benefits at a level
equal to those benefits provided by Sections 11.0112 and 11.0113 of this Contract for each retired
employee to age sixty-five.” 

Plan Descriptions. OEA, like other employers, distributes summary plan
descriptions to its employees to assist them in understanding the more detailed, complex and formal
plan documents. Each of the summaries distributed to the plaintiffs contained reservation-of-rights
clauses.
        The summary distributed to the OASU retirees provided: “Retired employees may continue
coverage, in accordance with the collective bargaining agreement . . . . While the employer expects
retiree coverage to continue, the employer reserves the right to modify or discontinue retiree
coverage at any time.” JA 1832. Elsewhere the OASU summary said that OEA “may modify or
amend the Plan from time to time in accordance with the provision of the collective bargaining
agreement.” JA 1851.
No. 06-4393           Prater et al. v. Ohio Education Association                             Page 3


        The reservation-of-rights clauses in the PSU summaries did not say that any modifications
to benefits must be in accordance with the bargaining agreements. “The Plan Administrator,” they
said, “may change or eliminate benefits under the plan and may terminate the entire plan or any
portion of it.” JA 1934 (Thorley); JA 1976 (Prater); see also JA 2045 (Westfall).
       The Dispute. For two decades, OEA provided most of its retirees with insurance to
supplement Medicare after they reached 65. On March 1, 2004, OEA sent a letter to PSU employees
informing them that OEA would honor its “contractual commitment[]” to reimburse retirees for
Medicare Part B but would no longer pay for the “optional, supplemental coverage” it had been
providing. JA 98. That same day, OEA sent a similar letter to OASU retirees, informing them that
“OEA’s obligation to provide coverage ceases” when each retiree reaches the age of 65. JA 138.
On August 31, 2004, OEA terminated the retirees’ supplemental coverage.
       The OASU and PSU retirees filed this class action under Section 301 of the Labor
Management Relations Act, claiming that the union had violated the collective bargaining
agreements. OEA moved for summary judgment on the PSU retirees’ claims for post-65
supplemental insurance, and it moved for summary judgment or partial summary judgment on the
OASU retirees’ claims for prescription drug, surgical, hospitalization and outpatient coverage. After
the parties had filed their summary judgment papers, the retirees sought leave to amend their
complaint to add several ERISA claims.
        The district court held that the contracts unambiguously excluded the sought-after coverage.
It reasoned that the “to age 65” clause in the PSU agreement “indicates a limitation on coverage
available and is not at all ambiguous.” D. Ct. Op. at 11. And it reasoned that the OASU agreement
contained a “limitation on coverage [that] could not be more clear or unambiguous.” 

The
court also held that the plan summaries reserved to OEA an unqualified right to alter or terminate
the retirement benefits under 

, and ultimately granted OEA’s motion for
summary judgment on all claims. D. Ct. Op. at 15–16. The court denied the retirees’ motion for
leave to amend because the litigation was at an advanced stage.
                                                 II.
        At the same time that ERISA carefully regulates the vesting of pension benefits, it leaves the
decision of whether employers will provide employees with healthcare benefits upon retirement to
contract—a contract that may come in the form of a collective bargaining agreement, an at-will
employment relationship or something in between. See UAW v. Yard-Man, Inc., 

,
1479 (6th Cir. 1983); Sprague v. Gen. Motors Corp., 

, 400 (6th Cir. 1998); Yolton v.
El Paso Tenn. Pipeline Co., 

, 579–80 (6th Cir. 2006). In the past, the application of
“ordinary principles of contract interpretation” to these different types of agreements, 

, has raised a host of perplexing questions: What is required to establish an employer’s
commitment to provide lifetime benefits to retirees? What exactly are lifetime healthcare benefits?
Does a promise of lifetime benefits mean that they cannot be reduced over the life of a retiree?
What if the employer reduces health benefits for active employees or increases the cost of those
benefits to active employees? What if the employer increases some health benefits for active
employees but reduces others? Must the retiree take the bitter with the sweet? Or is it a
ratchet—with only the improvements in health benefits available to the retiree but with no
compulsion to take any reduction?
        Happily for us, this case sidesteps these questions—at least for now. OEA concedes that,
in the absence of a right to terminate retiree benefits under the reservation-of-rights clauses in the
summary plan descriptions, a fact dispute exists over whether the retiree benefits provided for in the
collective bargaining agreements survive the term of the agreements. That leaves two related but
distinct disputes for us to resolve: (1) Are the retirees’ claimed benefits among those enumerated
No. 06-4393           Prater et al. v. Ohio Education Association                              Page 4


in the collective bargaining agreements? (2) Did OEA’s plan summaries give the union the right
to terminate any health benefits provided for in the collective bargaining agreements?
                                                  A.
        In interpreting collective bargaining agreements, we consider the language of the agreement,
the context in which that language appears and other traditional canons of construction. McCoy v.
Meridian Auto. Sys., 

, 422 (6th Cir. 2004). If, after applying these rules of
interpretation, the contract remains ambiguous, we permit the parties to introduce extrinsic evidence
about their original understanding of the contract’s terms. 

issue with respect to the OASU retirees is whether OEA committed to provide them with
lifetime prescription drug benefits. In concluding that OEA made no such promise, the district court
accepted the following chain of reasoning: (1) when the OASU retirees left active employment, the
collective bargaining agreement said that, “[a]fter the retiree reaches age 65, the Association is
required to provide only major-medical coverage,” JA 1086; (2) the benefits provided to active
employees under the collective bargaining agreement at that time fell into distinct categories:
“hospitalization; surgical; major-medical; out-patient X-ray; EKG; laboratory; prescription drug;
dental; and optical,” 

(emphases added); and (3) the independent provision for
“prescription drug” and “major-medical” coverage for active employees suggests that, when OEA
said it would “provide only major-medical coverage” for retirees, it would not provide prescription
drug coverage for them.
         In one sense, we accept this chain of reasoning as well. The explicit limitation of healthcare
benefits for retirees to “major-medical” plainly indicates that OEA did not commit to provide
“prescription drug” coverage as well. But this limitation means only that the promise of major-
medical coverage does not include the formal package of benefits provided under the “prescription
drug” heading in the agreement. It does not mean that “major-medical” may never include
prescription drugs. It shows only that major-medical insurance should not be interpreted to provide
the retirees the same level of prescription drug coverage they had enjoyed prior to age 65. When
retirees suffer a “major-medical” illness or injury, the contract is at least ambiguous as to whether
OEA will provide the retirees with coverage for the drugs necessary to treat that condition.
         The OASU retirees have presented extrinsic evidence backing up this position. Although
the retirees’ summary plan description also contains a section for a “Prescription Drug Program,”
JA 1823, distinct from the section for “Major Medical Benefits,” JA 1816, the major-medical section
explicitly provides some coverage for “prescription drugs as specified in the Schedule of Benefits,”
JA 1820. Notes from the contract negotiations also indicate that drug and major-medical coverages
overlap. In the face of this language of the agreement and this extrinsic evidence, summary
judgment cannot be granted to OEA solely on the basis of the scope of benefits outlined in the
collective bargaining agreement.
                                                  2.
        The pertinent PSU collective bargaining agreement’s provision for post-65 retiree benefits
also raises material ambiguities. Here are the relevant provisions:
No. 06-4393           Prater et al. v. Ohio Education Association                              Page 5


       11.0141         Continuation of Benefits
                       The Association shall continue to provide all benefits provided [for active
                       employees] by Sections 11.0112 and 11.0113 of this Contract for each retired
                       employee to age sixty-five (65).
       11.0142         Reimbursement for Cost of Medicare
                       The Association shall reimburse each retired employee over age sixty-five
                       (65) for the cost of Medicare Part B.
       11.0143         Supplement to Medicare
                       The Association shall supplement the benefits of Medicare Parts A and B to
                       provide benefits at a level equal to those benefits provided by Sections
                       11.0112 and 11.0113 of this Contract for each retired employee to age sixty-
                       five (65).
JA 1357; JA 1468; JA 1547–48.
        The question, as framed by the parties, is whether the clause “to age sixty-five” in the
“Supplement to Medicare” subsection cuts off coverage after age 65. As OEA sees it, the “to age
sixty-five” clause in the “Continuation of Benefits” subsection plainly places a limit on liability and
accordingly the same clause must be read the same way in the “Supplement to Medicare”
subsection. The PSU retirees respond that the latter half of the “Supplement to Medicare”
subsection must be interpreted as a comparative clause under which OEA commits to provide
retirees with coverage “equal to” that which they had been given up “to age sixty-five.”
         Although courts “should construe terms so as to render none nugatory and avoid illusory
promises,” 

(internal quotation marks omitted), the task is not always that
easy: Inartful drafting sometimes leaves courts with competing interpretations that both render other
provisions of the contract superfluous or at least awkward. This is such a case. On the one hand,
the retirees’ interpretation renders the same phrase—“to age sixty five”—as a limit on coverage in
one subsection and almost meaningless two subsections later. On the other hand, OEA’s
interpretation creates problems of its own. Reading “to age sixty-five” to cut off coverage at 65 in
both provisions renders the promise of a “Supplement to Medicare” meaningless because the
“Continuation of Benefits” subsection already promises PSU retirees that same level of coverage
up to age 65. Although OEA hypothesizes that this provision allows them to take advantage of
government benefits to fulfill that duty, the “Supplement to Medicare” provision is structured as an
obligation rather than something the union may do. As a general rule, moreover, only people with
disabilities may receive Medicare before age 65, and OEA’s interpretation renders a subsection that
appears to be applicable to all retirees relevant only to a small subset of them. Also supporting the
retirees’ reading is the fact that all of the language following the “equal to” phrase parrots the
language in the “Continuation of Benefits” subsection, suggesting that the clause has a comparative,
not a restrictive, purpose to it.
        As we see it, then, the agreement is at least ambiguous when it comes to whether it provides
post-65 supplemental insurance. The extrinsic evidence—the affidavits submitted by the retirees
and OEA’s consistent practice of providing supplemental insurance—sufficiently supports the PSU
retirees’ position to raise a material factual dispute over the meaning of the pertinent contract.
No. 06-4393           Prater et al. v. Ohio Education Association                             Page 6


                                                 B.
       The district court also held that OEA reserved the right to terminate or modify benefits
through several summary plan descriptions. We disagree.
        As a general rule, “an existing contract cannot be unilaterally modified.” Baptist Physician
Hosp. Org., Inc. v. Humana Military Healthcare Servs., Inc., 

, 350 (6th Cir. 2007); see
also Nagle Heating & Air Conditioning Co. v. Heskett, 

, 868 (Ohio Ct. App. 1990)
(“A contract cannot be unilaterally modified.”); 17A C.J.S. Contracts § 410 (“A signed
contract . . . cannot be changed without the consent or subsequent agreement of the parties.”). Were
it otherwise, the option of either party to modify a contract unilaterally would defeat the essential
purpose of reaching an agreement in the first place—to bind the parties prospectively.
        This principle applies with equal force to collective-bargaining agreements, where employers
are statutorily barred from effectuating “unilateral modification[s] of . . . existing collective
bargaining agreement[s].” N.L.R.B. v. Ford Bros., Inc., 

, 233 (6th Cir. 1986) (per
curiam). Even when an employer enters bankruptcy, the law “prohibits the employer from
unilaterally modifying any provision of the collective bargaining agreement.” In re Unimet Corp.,

, 884 (6th Cir. 1988); see 11 U.S.C. § 1113.
        One of our decisions, Maurer, complicates matters. There, we held that a summary plan
description, issued after a collective bargaining agreement had been signed, prevented retiree
benefits from vesting because it reserved the right of the employer to “curtail or eliminate coverage
for any treatment, procedure, or service regardless of whether [the employee is currently] receiving
treatment.” 

. Because the reservation of rights was conspicuous and
unqualified, we held, “the Union was obligated to grieve or enter suit” if it disagreed with the
employer’s assertion of authority—even if that assumption of authority came after the effective date
of the relevant collective bargaining agreement. 

(internal quotation marks omitted).
        In McCoy, we limited Maurer to “unqualified reservation-of-rights 

, that claims a “unilateral right by the employer to terminate coverage without regard to existing
or future collective bargaining agreements,” 

Because the summary at issue in McCoy said
that any “termination” of benefits was “subject to the provisions of any applicable collective
bargaining agreement,” we held that it could not “fairly . . . have prompted the union immediately
to protest.” 

(internal quotation marks omitted). McCoy, we acknowledge, involved a
preliminary-injunction decision and thus turned on our review of a likelihood-of-success
determination, not a final merits determination. But we stand by this clarification of Maurer
because a broad reading of the decision would run headlong into the rule that a plan summary
“cannot vitiate contractually vested or bargained-for-rights.” Halliburton Co. Benefits Comm. v.
Graves, 

, 378 (5th Cir. 2006) (“[A] reservation-of-rights clause in a plan document,
which allows a company to amend or terminate a plan at any time, cannot vitiate contractually
vested or bargained-for rights.”) (internal quotation marks omitted). To our knowledge, no court
of appeals has forced unions to file grievances in the face of a summary plan description that
purported to remove a promise of lifetime health benefits.
         As in Maurer, OEA’s summary plan descriptions contained reservation-of-rights language.
See JA 1832 (OASU summary stating that “[w]hile the employer expects retiree coverage to
continue, the employer reserves the right to modify or discontinue retiree coverage at any time”);
JA 1934 (PSU summary reserving the right to “change or eliminate benefits under the plan
and . . . terminate the entire plan or any portion of it”). But unlike Maurer, these clauses were not
sufficiently unqualified to “fairly . . . have prompted the union immediately to protest.” 

. As in McCoy, neither summary explicitly represented to the retirees that existing
medical treatment could be cut off, as the summary in Maurer did. See 

And as in McCoy,
No. 06-4393           Prater et al. v. Ohio Education Association                              Page 7


the OASU summary explicitly claimed to be established “in accordance with a collective bargaining
agreement,” JA 1801, and referenced the bargaining agreement every time it mentioned potential
modifications.
        Perhaps most importantly, both the PSU and OASU agreements say that the contracts
represent the full commitments between the parties and that the agreements cannot be amended
without signed, mutual consent, a clause never mentioned, much less discussed, with respect to the
Maurer collective bargaining agreement. When a contract contains formal procedures requiring
mutual, written assent to amend, that language preempts future unilateral termination of rights. See
Pleasantview Nursing Home, Inc. v. N.L.R.B., 

, 754 (6th Cir. 2003) (holding that oral
modification of a collective bargaining agreement was ineffective in the presence of “an express
zipper clause prohibiting modification except by written agreement”); Martin Marietta Energy Sys.,
Inc. v. N.L.R.B., No. 87-5369, 

, at *3–4 (6th Cir. Mar. 17, 1998) (per curiam)
(affirming NLRB’s finding of unfair labor practice when an employer’s “unilateral action” breached
a collective bargaining agreement’s formal amendment clause and rejecting an argument that the
union waived its right to complain through inaction). On this record, the unions thus could not fairly
be “compelled to protest the SPD language,” 

—at least when the summary
does not explicitly renounce the collective bargaining agreement—because both sets of contracts
explicitly said that their bargained-for rights could not be terminated in such a manner. The
summaries instead serve as extrinsic evidence regarding the extent of the employer’s promise of
future healthcare benefits and whether the parties intended the benefits to vest. See 

–82. They cannot, however, be interpreted to permit the unilateral termination of these
alleged contractual rights.
                                                 III.
        The retirees also challenge the district court’s denial of their motion for class certification
and their motion to amend their complaint. As to the first motion, the court premised its denial of
the class-certification motion on its summary judgment decision. D. Ct. Op. at 16. We accordingly
remand the case to the district court to address class certification in the first instance.
         As to the second motion, the district court did not abuse its discretion. See Leary v.
Daeschner, 

, 904 (6th Cir. 2003) (“Denial of a motion for leave to amend is reviewed
by this court for an abuse of discretion.”). Leave to amend, it is true, should be “freely given when
justice so requires,” but it can be denied on the basis of “undue delay, bad faith or dilatory
motive . . . [or] futility of amendment.” Foman v. Davis, 

, 182 (1962) (internal
quotation marks omitted); see also Fed. R. Civ. P. 15. And our court, it is also true, has required “at
least some significant showing of prejudice” to deny a motion to amend based solely upon delay.
Moore v. City of Paducah, 

, 562 (6th Cir. 1986) (per curiam). Taken together,
however, the retirees’ delay, the late stage of the case when the motion was filed and the likely
futility of any amendment show that the district court acted well within its discretion.
         The timing of the motion undermines plaintiffs’ position. They moved for leave to amend
on January 13, 2006, nine months after the amendment deadline created by the magistrate judge’s
pretrial order. By the time the retirees filed the motion, the parties had fully briefed the summary
judgment motions and exchanged a substantial number of documents through discovery. Even if
the retirees were not aware of their potential ERISA claims at the outset of the litigation, they had
sufficient information to bring these claims long before they filed their motion.
        The requested amendment also would have added little, if any, value to their complaint. The
retirees acknowledge that their proposed ERISA claim “parallel[s]” their existing LMRA claim, Br.
at 43, because the two claims rise or fall on the same contractual terms, see Teamster’s Local 348
Health & Welfare Fund v. Kohn Beverage Co., 

, 317 n.2 (6th Cir. 1984) (noting that,
No. 06-4393           Prater et al. v. Ohio Education Association                             Page 8


where an obligation arises “under the collective bargaining agreement[,] . . . the inquiry relative to
both the LMRA claims and ERISA claims is identical”). To the extent the retirees hope to raise
distinct breach-of-fiduciary-duty claims under ERISA, that claim almost assuredly would be futile.
See Curtiss-Wright Corp. v. Schoonejongen, 

, 78 (1995) (“[A] company does not act in
a fiduciary capacity when deciding to amend or terminate a welfare benefits plan.”) (quoting Adams
v. Avondale Indus., Inc., 

, 947 (6th Cir. 1990)).
                                                 IV.
        For these reasons, we reverse the district court’s grant of summary judgment, affirm its
denial of the plaintiffs’ motion to amend their complaint and remand for further proceedings.