FOR PUBLICATION
 UNITED STATES COURT OF APPEALS
      FOR THE NINTH CIRCUIT

AARON CAIN MCKNIGHT,                     No. 08-55459
            Petitioner-Appellant,
              v.                            D.C. No.
                                          2:07-cv-05541
ADAM N. TORRES, U.S. Marshal,
                                            OPINION
           Respondent-Appellee.
                                    
       Appeal from the United States District Court
           for the Central District of California
       Christina A. Snyder, District Judge, Presiding

                 Argued and Submitted
          March 10, 2009—Pasadena, California

                   Filed April 20, 2009

   Before: Michael Daly Hawkins, Marsha S. Berzon and
            Richard R. Clifton, Circuit Judges.

                Opinion by Judge Hawkins




                           4549
                     MCKNIGHT v. TORRES                  4551




                         COUNSEL

William J. Genego, Nasatir, Hirsch, Podberesky & Genego,
Santa Monica, California, for the petitioner-appellant.

Daniel Scott Goodman, Assistant United States Attorney,
Deputy Chief, Criminal Division, Los Angeles, California, for
the respondent-appellee.


                         OPINION

HAWKINS, Circuit Judge:

   In this international extradition case, Aaron Cain McKnight
(“McKnight”) appeals the denial of his 28 U.S.C. § 2241
habeas corpus petition, arguing the government violated the
covenant of good faith and fair dealing implied in his immu-
nity agreement with the United States Attorney’s Office for
the Central District of California (the “U.S. Attorney”).
According to McKnight, he “reasonably expected” the gov-
ernment, having granted immunity from use of his incriminat-
ing admissions against him in any United States prosecution,
would not disseminate his admissions to any foreign jurisdic-
tions for prosecution abroad. Concluding the government’s
actions did not violate the immunity agreement, we affirm.

                   I.   BACKGROUND

A.   Factual Background

  A federal grand jury issued an indictment charging fourteen
individuals, including McKnight, with various offenses
4552                 MCKNIGHT v. TORRES
related to the importation of an illicit substance commonly
known as Ecstasy from France into the United States. Shortly
after the indictment, McKnight agreed to cooperate with the
U.S. Attorney in exchange for “direct use immunity” against
use of any statements he made in a prosecution against him
by the U.S. Attorney.

   Prior to McKnight’s proffer session, he and the U.S. Attor-
ney executed a written agreement in which he agreed to
answer questions “truthfully and completely” in exchange for
the government’s promise “not to offer in evidence in its case-
in-chief or for the purpose of any sentencing hearing, any
statements made by [McKnight] at the meeting” in either “the
above-captioned case [or] in any other prosecution that may
be brought against [McKnight] by this Office.” McKnight
made incriminating statements during the proffer session
regarding his recruitment of young American women to
import Ecstasy into the United States.

  The government made no use of McKnight’s proffer state-
ments in his criminal trial, which resulted in a hung jury. The
grand jury subsequently issued a superseding indictment, pur-
suant to which McKnight pled guilty to seven counts and was
sentenced to 100 months in prison.

   Around the same time, the Tribunal de Grande Instance de
Paris issued a judgment following trial in abstentia, convict-
ing and sentencing McKnight of various crimes related to his
Ecstasy trafficking. Among the evidence used in the French
prosecution was an “investigation report concerning the depo-
sition” of McKnight by United States authorities. The “depo-
sition” was, in fact, McKnight’s proffer statement to the U.S.
Attorney. On the same day he was sentenced in the United
States court, McKnight was taken into custody pursuant to a
provisional extradition arrest warrant, issued at the request of
the French government under the Extradition Treaty.
                     MCKNIGHT v. TORRES                  4553
B.   Procedural Background

   The United States government thereafter filed an extradi-
tion complaint on behalf of France. McKnight responded to
the complaint, arguing, among other things, that the govern-
ment had breached its immunity agreement by sharing his
incriminating admissions with the French government. The
magistrate judge rejected the argument, concluding that the
language of the immunity agreement was not ambiguous—
“[i]t means exactly what it says”—and by its “express terms”
immunized “McKnight’s statements only from being offered
in evidence in the government’s case-in-chief or for sentenc-
ing purposes.” Because the French prosecution “was not
brought by the [U.S. Attorney],” and was instead “brought by
the Republic of France in its capacity as sovereign,” the
immunity agreement had not been violated. Rejecting
McKnight’s remaining arguments, the extradition magistrate
judge found McKnight extraditable to France and certified the
matter to the U.S. Secretary of State.

   McKnight filed this § 2241 habeas petition challenging the
extradition order, arguing (1) the government breached its
immunity agreement with McKnight by sharing his incrimi-
nating statements with France, (2) his extradition was pre-
cluded by the Extradition Treaty because he was already
convicted in the United States, and (3) France lacked probable
cause to support extradition.

   The district court denied the petition. The court reasoned
that “the immunity agreement unambiguously applies exclu-
sively to criminal cases brought by the [U.S. Attorney]
against petitioner in its role as prosecutor for the United
States.” Because the language was not ambiguous, the district
court concluded, the plain terms of the agreement govern, and
the agreement was not breached. McKnight timely appealed,
challenging only the district court’s decision with respect to
the government’s alleged breach of the immunity agreement.
4554                  MCKNIGHT v. TORRES
              II.   STANDARD OF REVIEW

  We review de novo whether the district court erred in deny-
ing a habeas corpus petition challenging certification of an
extradition order; we review factual questions, as determined
by the extradition magistrate judge, for clear error. Man-Seok
Choe v. Torres, 

, 741 (9th Cir. 2008); Quinn v.
Robinson, 

, 791-92 (9th Cir. 1986).

   Here, “[b]ecause this is a claimed immunity agreement,
ordinary contract principles apply.” United States v. Wilson,

, 1059 (9th Cir. 2004) (citing United States v.
Plummer, 

, 802-03 (9th Cir. 1991)). “Whether
the facts establish a violation of the contract is a question of
law reviewed de novo.” 

Comstock & 

).

                     III.   DISCUSSION

   [1] We agree that the words of McKnight’s immunity
agreement were clear, explicit, and unambiguous. McKnight
concedes as much. He acknowledges that “the [U.S. Attor-
ney’s] dissemination of the proffer was not expressly prohib-
ited by the agreement,” and that, at the time he signed the
agreement, he recognized he “had to take the risk that his
[statement might become] known and available to some other
jurisdiction [that] could then use his statements to incriminate,
and convict, him.” He further admits that the U.S. Attorney’s
agreement not to use his statements “was limited to the pend-
ing prosecution and any other prosecution [the U.S. Attorney]
might bring against [him],” and that it did not reflect any
promise by the government either to disclose or not to dis-
close his statements “to other jurisdictions.”

    [2] The unambiguous words of the agreement are the end
of the story. “ ‘As a rule, the language of an instrument must
govern its interpretation if the language is clear and explic-
it.’ ” Brookwood v. Bank of Am., 

,
                        MCKNIGHT v. TORRES                         4555
1670-71 (Cal. Ct. App. 1996) (quoting Ticor Title Ins. Co. v.
Rancho Santa Fe Assn., 

. 726, 730 (Cal. Ct.
App. 1986)); see also Yount v. Acuff Rose-Opryland, 

, 835-36 (9th Cir. 1996) (“[W]hen a contract has been
reduced to writing, a court must ascertain the parties’ intent
from the writing alone.”). Because the agreement here was
clear, we must determine its meaning by reference to the par-
ties’ “ ‘objective intent, as evidenced by the words of the con-
tract.’ ” Cedars-Sinai Med. Ctr. v. Shewry, 

, 980 (Cal. Ct. App. 2006) (quoting Founding Members of
the Newport Beach Country Club v. Newport Beach Country
Club, Inc., 

, 956 (Cal. Ct. App. 2003)).
Accordingly, the parties’ “uncommunicated subjective intent
is irrelevant.” Reigelsperger v. Siller, 

, 579
(2007). Here, McKnight’s unambiguous agreement with the
government does not contain any limitation on the govern-
ment’s freedom to share his admissions with France. The U.S.
Attorney’s disclosure therefore did not violate the agreement.1

   McKnight nevertheless argues that the implied duty of
good faith and fair dealing “supplement[s]” the immunity
agreement, incorporating his “reasonabl[e] expect[ation] that
the [U.S. Attorney] would . . . not facilitate his proffer being
used by another jurisdiction.” In his view, the government’s
disclosure “frustrated” the “promise” of “protection” made to
him by the U.S. Attorney. This argument fails because it pre-
sumes away the dispute—i.e., that the “protection” offered by
the U.S. Attorney included protection from prosecution
abroad. This broad construction of the “protection” offered
simply is not reflected in the clear language of the agreement.

   Assuming arguendo that the implied duty of good faith and
fair dealing applies here, it “ ‘is limited to assuring compli-
  1
    McKnight never argued, either before the district court or on appeal,
that the U.S. Attorney’s extradition proceedings on behalf of France con-
stituted a violation of the direct use immunity agreement, so we do not
decide whether it did.
4556                  MCKNIGHT v. TORRES
ance with the express terms of the contract, and cannot be
extended to create obligations not contemplated by the con-
tract.’ ” Spinks v. Equity Residential Briarwood Apartments,

, 476 (Cal. Ct. App. 2009) (quoting Pasa-
dena Live v. City of Pasadena, 

, 1094
(Cal. Ct. App. 2004)). The condition operates only to prevent
a party from taking an action that “ ‘will injure the right of the
other to receive the benefits of the agreement.’ ” Major v. W.
Home Ins. Co., 

, 1209 (Cal. Ct. App.
2009) (quoting Gruenberg v. Aetna Ins. Co., 

,
573 (1973)). It neither “alter[s] specific obligations set forth
in the contract” nor “add[s] duties independent of the contrac-
tual relationship.” Shawmut Bank, N.A. v. Kress Assocs., 

, 1503 (9th Cir. 1994) (applying California law).

  [3] In this case, while McKnight may have hoped the U.S.
Attorney would not disclose his statements to the French
authorities, there is nothing in the plain words of the agree-
ment that provided that protection, and the implied covenant
of good faith simply cannot be employed to read it into the
agreement.

                    IV.    CONCLUSION

   [4] Future government witnesses are on notice that, if they
wish to prevent federal prosecutors from sharing incriminat-
ing statements with other sovereigns (including, for example,
the State governments), they must reduce that expectation to
writing. Conversely, prosecutors should not be surprised
when such protection is sought by cooperating witnesses, or
when, if such protection is refused, witnesses decline the
agreement. Because there was no written agreement prevent-
ing disclosure of the statements here, however, the govern-
ment did not breach the agreement. See United States v. Chiu,

, 626 (9th Cir. 1997).

  AFFIRMED.