                         PUBLISHED

UNITED STATES COURT OF APPEALS
               FOR THE FOURTH CIRCUIT


DAVID YI,                              
               Petitioner-Appellant,
                v.
FEDERAL BUREAU OF PRISONS;
VANESSA P. ADAMS, Warden of FCI-
Petersburg,                                   No. 04-6891
            Respondents-Appellees.


THE OFFICE OF THE FEDERAL PUBLIC
DEFENDER,
      Amicus Supporting Appellant.
                                       
          Appeal from the United States District Court
        for the Eastern District of Virginia, at Richmond.
                 Robert E. Payne, District Judge.
                          (CA-03-436)

                     Argued: March 18, 2005

                     Decided: June 17, 2005

   Before WILLIAMS, MOTZ, and DUNCAN, Circuit Judges.



Affirmed by published opinion. Judge Duncan wrote the opinion, in
which Judge Williams and Judge Motz joined.


                           COUNSEL

ARGUED: Mark Owen Gabrielson, HOLLAND & KNIGHT, L.L.P.,
Seattle, Washington, for Appellant. Tara Louise Casey, Assistant
2                 YI v. FEDERAL BUREAU OF PRISONS
United States Attorney, OFFICE OF THE UNITED STATES
ATTORNEY, Richmond, Virginia, for Appellees. Sarah Sargent Gan-
nett, OFFICE OF THE FEDERAL PUBLIC DEFENDER, Baltimore,
Maryland, for Amicus Curiae. ON BRIEF: Christopher H. Howard,
HOLLAND & KNIGHT, L.L.P., Seattle, Washington, for Appellant.
Paul J. McNulty, United States Attorney, Alexandria, Virginia, for
Appellees. James Wyda, Federal Public Defender, Baltimore, Mary-
land, for Amicus Curiae.


                             OPINION

DUNCAN, Circuit Judge:

   David Yi appeals from the district court’s order denying his peti-
tion for a writ of habeas corpus under 28 U.S.C. § 2241. Yi contends
that he has earned more credit for "Good Conduct Time" than the
Bureau of Prisons ("BOP") has awarded him under 18 U.S.C. § 3624,
a federal law that authorizes the BOP to reduce sentences for good
behavior. For the following reasons, we affirm.

                                  I.

   Under 18 U.S.C. § 3624, prisoners who "display[ ] exemplary com-
pliance with institutional disciplinary regulations" may earn credit
toward the service of their sentence. 18 U.S.C. § 3624(b)(1). Credit
for good conduct time ("GCT") is subtracted from the prisoner’s sen-
tence, such that the prisoner becomes eligible for release before serv-
ing the full sentence imposed by the sentencing court. 18 U.S.C.
§ 3624(a). The statute delegates authority to the BOP to calculate and
award GCT credits. In particular, subsection (b) provides that:

    [A] prisoner who is serving a term of imprisonment of
    more than 1 year[,] other than a term of imprisonment for
    the duration of the prisoner’s life, may receive credit toward
    the service of the prisoner’s sentence, beyond the time
    served, of up to 54 days at the end of each year of the pris-
    oner’s term of imprisonment, beginning at the end of the
    first year of the term, subject to determination by the Bureau
                    YI v. FEDERAL BUREAU OF PRISONS                       3
      of Prisons that, during that year, the prisoner has displayed
      exemplary compliance with institutional disciplinary regula-
      tions. . . . [I]f the Bureau determined that, during that year,
      the prisoner has not satisfactorily complied with such insti-
      tutional regulations, the prisoner shall receive no such credit
      toward service of the prisoner’s sentence or shall receive
      such lesser credit as the Bureau determines to be appropri-
      ate. . . . [C]redit for the last year or portion of a year of the
      term of imprisonment shall be prorated and credited within
      the last six months of the sentence.

18 U.S.C. § 3624(b)(1).

   Yi is currently serving a 151-month sentence for his role in a con-
spiracy to violate the Racketeer Influenced and Corrupt Organizations
Act. 18 U.S.C. § 1962. Yi has been incarcerated since November 21,
1994. Without credit for good behavior, he would be released upon
the expiration of his sentence on June 22, 2007.

   The BOP has determined, however, that Yi can earn a maximum
of 592 days of credit against his sentence under 18 U.S.C. § 3624.
The BOP arrives at this figure by awarding up to 54 days’ GCT for
each year the inmate serves in prison. For example, before this litiga-
tion commenced, Yi served more than eight years of his 151-month
sentence. After each year in prison, Yi received a credit of 54 days
toward the service of his sentence for good behavior. Consequently,
after serving eight years of his sentence, Yi accumulated a total of
432 days’ GCT. Barring any disciplinary action, the BOP projects that
Yi will earn an additional 160 days’ GCT as he serves out the remain-
der of his sentence.1 Thus, the BOP expects to award Yi a total of 592
days’ GCT under 18 U.S.C. § 3624. After subtracting the total
amount of GCT that can be earned on his 151-month sentence, the
  1
   The 160 days are computed as follows: Yi can earn a maximum of
108 days after serving his ninth and tenth year of imprisonment. In addi-
tion, he can earn a prorated amount of 52 days for the last portion of a
year that he serves. As noted earlier, Yi will not serve the full 151
months of the sentence imposed; each annual GCT award reduces the
amount of time that he will ultimately serve.
4                  YI v. FEDERAL BUREAU OF PRISONS
BOP has determined that Yi will become eligible for release on
November 7, 2005.

   The BOP’s method of calculating GCT appears in BOP Program
Statement 5880.28, which is part of the agency’s Sentencing Compu-
tation Manual. The BOP has also promulgated a rule, pursuant to the
notice and comment procedures of the Administrative Procedure Act,
5 U.S.C. § 553, setting forth its interpretation of the GCT statute. The
rule states that "[p]ursuant to 18 U.S.C. § 3624(b), . . . an inmate
earns 54 days credit toward service of sentence (good conduct time
credit) for each year served." 28 C.F.R. § 523.20.

   Yi contends that the BOP’s method of calculating GCT is contrary
to the plain language of 18 U.S.C. § 3624. He argues that by using
the phrase "term of imprisonment" in subsection (b), Congress
intended that the agency award GCT based upon the length of the sen-
tence imposed, not time actually served. Stated differently, Yi con-
tends that "term of imprisonment" in subsection (b) means "sentence
imposed," not "time served." Accordingly, Yi argues that the BOP
must calculate GCT by multiplying his 151-month sentence by 54,
which results in a maximum of 679 days2 of credit and his release in
August of 2005.

   Importantly, under Yi’s interpretation of 18 U.S.C. § 3624, he is
not required to serve a full year before he can receive credit for good
behavior. Yi contends that the statute’s plain language entitles him to
receive up to 54 days of credit within any given year of his sentence.
Thus, in the first year of his sentence, if Yi exhibits good conduct for
311 days, he would receive 54 days of credit. On the other hand, the
BOP awards credit when it determines that an inmate has demon-
strated a full year of compliance with prison disciplinary regulations.3
    2
    151 months/12 = 12.583 x 54 = 679 days’ GCT.
    3
    A prisoner may receive a prorated credit before serving a full year if
the potential award of GCT credit would reduce his actual time served
to less than a year. 28 C.F.R. § 523.20. For example, a prisoner serving
a term of imprisonment of 366 days (the shortest term eligible for GCT
under the statute) cannot wait until he has served a full year before
receiving credit earned for good behavior. The credit due this inmate (54
                   YI v. FEDERAL BUREAU OF PRISONS                       5
   Yi filed the instant habeas petition under 28 U.S.C. § 2241, assert-
ing that the BOP calculates GCT in a manner that is contrary to 18
U.S.C. § 3624. The district court denied relief on the grounds that the
plain language of the statute requires the computation of GCT on the
basis of time actually served. In the alternative, the district court held
that the BOP’s construction of the statute was reasonable under Chev-
ron U.S.A., Inc. v. Natural Resources Defense Council, Inc., 467 U.S.
837 (1984).

  Yi now appeals.

                                    II.

   We review the district court’s order denying Yi’s habeas petition
de novo. Selgeka v. Carroll, 184 F.3d 337, 342 (4th Cir. 1999). In
Chevron, the Supreme Court established a two-step process to guide
judicial review of an agency’s interpretation of a statute. First, we
must determine whether the plain language of the statute directly
addresses the precise question before us. "If the intent of Congress is
clear, that is the end of the matter; for the court, as well as the agency,
must give effect to the unambiguously expressed intent of Congress."
Chevron, 467 U.S. at 842-43. However, if the statute is silent or
ambiguous in expressing Congress’ intent, we defer to the agency’s
reasonable construction of the statute. Id. at 843-44.

                                    A.

   In this case, the precise question before us is whether GCT must
be awarded based upon the length of a prisoner’s sentence or his time
actually served. Of course, "the first place we must look to see if Con-
gress has spoken to the issue with which we are concerned and
whether Congressional intent in that regard is clear is on the face of

days) would exceed the time remaining on his sentence of imprisonment
(one day). Recognizing this, the statute authorizes the BOP to award a
prorated credit of 47 days, reducing the inmate’s actual time served to
319 days. See Pacheco-Camacho v. Hood, 272 F.3d 1266, 1267-68 (9th
Cir. 2001) (discussing practice of awarding prorated credit for service of
less than a year).
6                  YI v. FEDERAL BUREAU OF PRISONS
the statute." Kofa v. INS, 60 F.3d 1084, 1088 (4th Cir. 1995) (en
banc). In determining whether a statute is clear, we are guided "by
reference to the language itself, the specific context in which that lan-
guage is used, and the broader context of the statute as a whole." Rob-
inson v. Shell Oil Co., 519 U.S. 337, 341 (1997).

   Yi contends that by directing the BOP to award "up to 54 days at
the end of each year of the prisoner’s term of imprisonment," Con-
gress plainly intended that the agency calculate GCT based upon the
sentence imposed, not time served. 18 U.S.C. § 3624(b)(1) (emphasis
added). Significant to his argument is the fact that the phrase "term
of imprisonment" appears three times within the first sentence of sub-
section (b):

    [A] prisoner who is serving a term of imprisonment of more
    than 1 year[,] other than a term of imprisonment for the
    duration of the prisoner’s life, may receive credit toward the
    service of the prisoner’s sentence, beyond the time served,
    of up to 54 days at the end of each year of the prisoner’s
    term of imprisonment . . . .

Id. (emphasis added).

   Without question, the first two references to "term of imprison-
ment" in subsection (b) refer to the sentence imposed. The statute
declares that the BOP may award credit only to prisoners serving a
term of imprisonment of more than one year, with the exception of
prisoners serving a life sentence. "In this part of the statute, ‘term of
imprisonment’ must . . . refer to the sentence [imposed] because the
Bureau has to determine whether a prisoner is eligible for the credit
on the first day he arrives in prison." White v. Scibana, 390 F.3d 997,
1001 (7th Cir. 2004). Invoking the parallelism canon of statutory con-
struction, Yi argues that a given term cannot change meanings within
the same sentence. See Brown v. Gardner, 513 U.S. 115, 118 (1994)
("[T]here is a presumption that a given term is used to mean the same
thing throughout a statute, a presumption surely at its most vigorous
when a term is repeated within a given sentence . . . .") (citation omit-
ted). Thus, Yi argues that "term of imprisonment" must also mean
"sentence imposed" when it is used for the third time in 18 U.S.C.
§ 3624(b). Several district courts have agreed with this reasoning and
                  YI v. FEDERAL BUREAU OF PRISONS                    7
have held that the statute unambiguously requires the calculation of
GCT based upon the sentence imposed. See Moreland v. Fed. Bureau
of Prisons, 363 F. Supp. 2d 882, 886 (S.D. Texas 2005), adopted by,
2005 U.S. Dist. LEXIS 6010 (S.D. Tex. March 31, 2005); Williams
v. DeWalt, 351 F. Supp. 2d 412, 418 (D. Md. 2004); White v. Scibana,
314 F. Supp. 2d 834, 841 (W.D. Wis. 2004), rev’d, 390 F.3d 997 (7th
Cir. 2004).

   We agree that Yi’s construction of 18 U.S.C. § 3624(b) is plausi-
ble; however, we do not agree that the statutory language unambigu-
ously compels this interpretation alone. In fact, no circuit court that
has addressed this issue has concluded that Yi’s interpretation of the
statute is compelled by its text. See White, 390 F.3d at 1002 ("[I]t is
impossible to make sense of 18 U.S.C. § 3624 while giving the phrase
‘term of imprisonment’ one meaning throughout."); see also
O’Donald v. Johns, 402 F.3d 172, 174 (3d Cir. 2005) (per curiam)
("[I]t is unclear whether the phrase ‘term of imprisonment,’ as used
several times in § 3624(b), refers to the sentence imposed or time
served."); Sample v. Morrison, No. 04-40698, 2005 U.S. App. LEXIS
4708, at *6-7 (5th Cir. March 22, 2005) (per curiam) (rejecting, in
dicta, contention that GCT statute requires computation of credit
based upon "sentence imposed"); Perez-Olivo v. Chavez, 394 F.3d 45,
49 (1st Cir. 2005) ("term of imprisonment" in GCT statute is ambigu-
ous); Pacheco-Camacho v. Hood, 272 F.3d 1266, 1268 (9th Cir.
2001) (statutory language unclear concerning whether GCT must be
awarded according to sentence imposed or time served).

   For example, in White, the Seventh Circuit observed that interpret-
ing "term of imprisonment" to mean "sentence imposed" in subsection
(b) conflicts with the fundamental purpose of the statute, which is to
award credit "at the end of each year" on account of the prisoner’s
good behavior "during that year." White, 390 F.3d at 1001. Specifi-
cally, the court explained that:

    The statute . . . establishes a process of awarding credit at
    the end of each year of imprisonment based on a review of
    the prisoner’s behavior during that year, a process that
    would be undermined if "term of imprisonment" means
    "sentence imposed." This is because the accumulation of
    good-time credit reduces the amount of time a prisoner will
8                  YI v. FEDERAL BUREAU OF PRISONS
      ultimately spend in prison, sometimes (as in White’s case)
      by more than an entire year. The Bureau cannot evaluate a
      prisoner’s behavior and award credit if the prisoner is not
      still in prison.

Id.

   The problem with awarding credit for every year of the "sentence
imposed" is illustrated in this case. After serving eight years of his
151-month sentence, Yi earned 432 days of GCT, reducing the time
that he will ultimately serve in prison by more than a year. After sub-
tracting 432 days from his sentence, Yi will serve no portion of the
last year of his sentence imposed. Nevertheless, Yi contends that an
inmate should receive GCT for every year (or partial year) of the sen-
tence imposed. However, to award credit for time not served would
conflict with Congress’ intent that prisoners "earn" credit under the
GCT statute by "display[ing] exemplary compliance with institutional
disciplinary regulations" during the year. 18 U.S.C. § 3624(b); see
also Sample, 2005 U.S. App. LEXIS 4708, at *3 ("[T]he statute
makes clear that good time credit must be earned by a prisoner on an
annual basis; it is not awarded in advance.") (emphasis added). An
inmate who is not in prison cannot "earn" credit for compliance with
prison disciplinary regulations.

  Other courts have noted that the interpretation advanced by Yi
would undermine the basic design of the statute. For example, the
Third Circuit has observed that:

      To calculate GCT based on the sentence imposed would
      allow an inmate to earn GCT for time he was not actually
      incarcerated. This unseemly result would frustrate the pro-
      cess and militates against finding that the phrase "term of
      imprisonment" unambiguously refers to the sentence
      imposed.

O’Donald, 402 F.3d at 174 (internal citation omitted). As another
court has explained:

      The statute awards GCT based upon BOP’s determination
      that "during that year" the prisoner complied with institu-
                  YI v. FEDERAL BUREAU OF PRISONS                     9
    tional disciplinary regulations. Such a directive requires that
    the prisoner has been incarcerated during that year so that
    his compliance may be measured. Therefore, granting GCT
    for years that will not be served is illogical, because compli-
    ance with disciplinary rules during those years is not possi-
    ble.

Pasciuti v. Drew, No. 9:04-CV-043(LEK), 2004 U.S. Dist. LEXIS
10352, at *17 (N.D.N.Y. June 2, 2004) (unpublished).

   Similarly, the statute authorizes the BOP to award lesser credit, or
none at all, if it determines that a prisoner has failed to comply with
disciplinary regulations "during [the] year." 18 U.S.C. § 3624(b)(1).
The statute therefore assumes that the prisoner has been incarcerated
during the year, such that the BOP can determine that his less than
satisfactory compliance with institutional regulations deserves less
than the full amount of credit authorized under the statute.

   For the same reason, Yi’s interpretation of the GCT statute also
conflicts with the mandate that "credit for the last year or portion of
a year of the term of imprisonment shall be prorated . . . ." 18 U.S.C.
§ 3624(b)(1) (emphasis added). Again, the accumulation of good
behavior credit often reduces the amount of time a prisoner serves by
more than an entire year. Consequently, the prisoner is released
before serving any portion of the last year of the sentence imposed
by the sentencing court. Thus, if we accepted Yi’s argument that
"term of imprisonment" means "sentence imposed," it would become
impossible to award prorated credit under the GCT statute without
awarding credit for time not served. As we have already concluded,
awarding credit for time not served would conflict with the funda-
mental design of the statute, which is to award credit "at the end of
each year" on account of the prisoner’s good behavior "during that
year." White, 390 F.3d at 1001; 18 U.S.C. § 3624(b)(1). Similarly, a
prisoner cannot "earn" a prorated credit for time not served. Sample,
2005 U.S. App. LEXIS 4708, at *3.

   Broadening our focus now to "the statute as a whole," Robinson,
519 U.S. at 341, we find that Congress clearly used the phrase "term
of imprisonment" to mean "time served" in a different subsection of
18 U.S.C. § 3624. Specifically, subsection (d) provides that:
10                 YI v. FEDERAL BUREAU OF PRISONS
     Upon the release of a prisoner on the expiration of the pris-
     oner’s term of imprisonment, the Bureau of Prisons shall
     furnish the prisoner with . . . suitable clothing[,] . . . an
     amount of money, not more than $500, . . . and . . . transpor-
     tation to the place of the prisoner’s conviction . . . .

18 U.S.C. § 3624(d). As Yi interprets the statute, a prisoner would
receive these benefits at the end of the "sentence imposed," which is
obviously too late in the case of an inmate who (as a result of annual
GCT credits) has been released from prison before serving the full
sentence imposed. In Yi’s case, the stipends would not be paid until
almost two years after his release. Clearly, Congress did not intend
this absurd result.

   Accordingly, we agree with the courts that have found ambiguous
the phrase "term of imprisonment" as it is used in 18 U.S.C. § 3624
to describe how GCT is awarded. We acknowledge the strong pre-
sumption that identical terms used in the same sentence of a statute
carry the same meaning. Brown, 513 U.S. at 118. However, as the
Supreme Court has explained, the

     presumption is not rigid and readily yields whenever there
     is such variation in the connection in which the words are
     used as reasonably to warrant the conclusion that they were
     employed in different parts of the act with different intent.

General Dynamics Land Sys., Inc. v. Cline, 540 U.S. 581, 595 (2004)
(internal quotations omitted). As the preceding analysis demonstrates,
we believe that this is precisely the case with respect to the phrase
"term of imprisonment" in 18 U.S.C. § 3624(b).

                                  B.

   Because the language of the statute is unclear, we may consult its
legislative history as a guide to congressional intent. United States v.
Rast, 293 F.3d 735, 737 (4th Cir. 2002) ("The confusing statutory lan-
guage allows us to look beyond the text for clues about congressional
intent."); see also Bedrock Ltd., LLC v. United States, 541 U.S. 176,
187 n.8 (2004) (noting that "longstanding precedents . . . permit resort
                    YI v. FEDERAL BUREAU OF PRISONS                    11
to legislative history only when necessary to interpret ambiguous stat-
utory text.").

   Principally, Yi argues that we must read 18 U.S.C. § 3624(b) to
require the computation of GCT based on the "sentence imposed"
because the prior version of the statute calculated GCT in this man-
ner. Under 18 U.S.C. § 4161 (repealed), a model prisoner could serve
less time by earning credit for good behavior against "the term of his
sentence." 18 U.S.C. § 4161 (repealed). In relevant part, this law pro-
vided that:

      Each prisoner convicted of an offense against the United
      States and confined in a penal or correctional institution for
      a definite term other than for life, whose record of conduct
      shows that he has faithfully observed all the rules and has
      not been subjected to punishment, shall be entitled to a
      deduction from the term of his sentence[,] beginning with
      the day on which the sentence commences to run . . . .

Id. In 1984, Congress repealed 18 U.S.C. § 4161 and codified the cur-
rent GCT statute as part of the Comprehensive Crime Control Act.
See Pub. L. No. 98-473, 98 Stat. 1976 (1984). Yi contends that noth-
ing in the language of the new statute or its legislative history sug-
gests that Congress intended to change the previous practice of
awarding GCT based upon the sentence imposed.

   We disagree. Although Congress was mainly concerned with sim-
plifying the computation of GCT under the prior statute,4 the new law
ended the practice of awarding credit "beginning on the day on which
the sentence commences to run[.]" 18 U.S.C. § 4161 (repealed). In the
current statute, Congress directs the BOP to award credit "beginning
at the end of the first year of the term[.]" 18 U.S.C. § 3624(b)(1)
(emphasis added). This revision of the statute is consistent with the
  4
   The previous system authorized different rates of GCT—five, six,
seven, eight, or ten days—depending upon the length of the sentence
imposed. 18 U.S.C. § 4161 (repealed). "An overarching purpose of the
new GCT statute was to make the computation of credit toward early
release pursuant to section 3624(b) considerably less complicated than
under [prior] law." Perez-Olivo, 394 F.3d at 50 (quotations omitted).
12                 YI v. FEDERAL BUREAU OF PRISONS
view, contrary to that advanced by Yi, that Congress intended to
replace the practice of computing GCT according to the sentence
imposed with a system that rewards inmates retrospectively "at the
end of each year" for compliance with disciplinary regulations "dur-
ing that year." 18 U.S.C. § 3624(b)(1). At best, the statute remains
unclear as to whether GCT should be awarded based upon time
served or the sentence imposed. Accordingly, we agree with the
courts that have held that the legislative history of the GCT statute
does not resolve the ambiguity in 18 U.S.C. § 3624(b). Perez-Olivo,
394 F.3d at 50 ("[T]he legislative history of the GCT statute . . . does
not indicate any congressional intent to calculate GCT based on ‘time
served’ or ‘sentence imposed.’"); Pacheco-Camacho, 272 F.3d at
1269-70 (legislative history of GCT statute does not remove ambigu-
ity).

                                   C.

   Having found that "term of imprisonment" in 18 U.S.C. § 3624(b)
is ambiguous, we must determine whether the BOP’s interpretation of
the statute is reasonable and therefore entitled to deference. Chevron,
467 U.S. at 843-44.5 In so doing, we "may not substitute [our] own
construction of [the] statutory provision for a reasonable interpreta-
tion made by the [BOP]." Id. at 844. Instead, we must uphold the
agency’s interpretation if it is "rational and consistent with the stat-
ute." NLRB v. United Food & Commercial Workers Union Local 23,
484 U.S. 112, 123 (1987).

   We conclude that the BOP has reasonably interpreted the statute so
as to require the calculation of GCT based upon the inmate’s time
  5
   "A precondition to deference under Chevron is a congressional dele-
gation of administrative authority." Adams Fruit Co. v. Barrett, 494 U.S.
638, 649 (1990). The BOP’s construction of the statute, which appears
in Program Statement 5880.28 and 28 C.F.R. § 523.20, "falls within the
implied statutory authority of the BOP." Pacheco-Camacho, 272 F.3d at
1270; see also White, 390 F.3d at 1001 ("The Bureau’s discretion to
resolve ambiguities in the good-time statute is implicit in its statutory
authority to determine and award good time and to release prisoners
when their sentences, as adjusted by the Bureau for good time credit,
have expired.").
                   YI v. FEDERAL BUREAU OF PRISONS                    13
served. The view that a prisoner should accrue 54 days of credit for
each 365 days of good behavior is consistent with Congress’ mandate
that the BOP reward a prisoner "at the end of each year" for good
behavior demonstrated "during that year." 18 U.S.C. § 3624(b)(1).
This language reflects "a clear congressional directive that the BOP
look retroactively at a prisoner’s conduct over the prior year, which
makes it reasonable for the BOP only to award GCT for time served."
Perez-Olivo, 394 F.3d at 53. Accordingly, we defer to the BOP’s rea-
sonable construction of 18 U.S.C. § 3624(b). Chevron, 467 U.S. at
843-44.

                                   D.

  Lastly, we consider Yi’s argument that the rule of lenity should
apply to resolve the ambiguity in 18 U.S.C. § 3624(b) in his favor.
We conclude that it should not.

   The rule of lenity holds that "where there is ambiguity in a criminal
statute,6 doubts are resolved in favor of the defendant." United States
v. Bass, 404 U.S. 336, 348 (1971). The rule applies "not only to
resolve issues about the substantive scope of criminal statutes, but to
answer questions about the severity of sentencing." United States v.
R.L.C., 503 U.S. 291, 305 (1992). "The rule of lenity is premised on
two ideas: First, a fair warning should be given to the world in lan-
guage that the common world will understand, of what the law
intends to do if a certain line is passed; second, legislatures and not
courts should define criminal activity." Babbitt v. Sweet Home Chap-
ter of Cmtys., 515 U.S. 687, 704 n.18 (1995) (internal quotations
omitted). Yi argues that, in light of these principles, we should read
18 U.S.C. § 3624 to require that the BOP calculate GCT according to
the sentence imposed.

   We need not resort to the rule of lenity in this case for two reasons.
First, BOP Program Statement 5880.28 and 28 C.F.R. § 523.20 pro-
vide the public with sufficient notice that GCT shall be awarded
  6
    We assume, without deciding, that 18 U.S.C. § 3624 is a "criminal
statute" in whose context the rule is properly invoked. See Perez-Olivo,
394 F.3d at 53 (expressing doubt concerning whether federal GCT law
is a "criminal" statute that invokes the rule of lenity).
14                 YI v. FEDERAL BUREAU OF PRISONS
based upon time actually served. Thus, while the language of the stat-
ute is ambiguous, the Program Statement and the regulation "give[ ]
the public sufficient warning to ensure that nobody mistakes the ambit
of the law or its penalties." Pacheco-Camacho, 272 F.3d at 1272; see
also Perez-Olivo, 394 F.3d at 53-54 (holding that rule of lenity does
not apply); O’Donald, 402 F.3d at 174 (same). Second, 18 U.S.C.
§ 3624 is a statute that Congress has charged the BOP to administer.
Rather than apply a presumption of lenity to resolve the ambiguity,
Chevron requires that we defer to the agency’s reasonable construc-
tion of the statute. "Chevron deference is a tool of statutory construc-
tion whereby courts are instructed to defer to the reasonable
interpretations of expert agencies charged by Congress to fill any gap
left, implicitly or explicitly, in the statutes they administer." America
Online, Inc. v. AT&T Corp., 243 F.3d 812, 817 (4th Cir. 2001) (inter-
nal quotations and emphasis omitted). As one court has explained:

     [D]eference trumps lenity when courts are called upon to
     resolve disputes about ambiguous statutory language, at
     least where the agency interpreting the criminal statute is:
     (1) responsible for administering the statute; and (2) that
     agency has promulgated its interpretation pursuant to the
     notice and comment provisions of the Administrative Proce-
     dure Act.

Sash v. Zenk, 344 F. Supp. 2d 376, 383 (E.D.N.Y. 2004). Thus, the
rule of lenity does not require that we adopt Yi’s interpretation of 18
U.S.C. § 3624(b).

  Accordingly, the district court’s order dismissing Yi’s petition for
a writ of habeas corpus is

                                                           AFFIRMED.
