The rule of lenity applies in criminal proceedings, while the "rule of narrow construction" applies in immigration proceedings. Each relates to construction of statutory provisions, and applies at different stages of the proceedings.
See Benefit of the Lori Rosenberg, Doubt: The Survival of the Principle of Narrow Construction and its Current Applications, 8 BENDER'S IMMIGR. BULL. 1553 (Oct. 1, 2003).

No "admission of guilt" was required under this domestic violence no-plea diversion statute. Penal Code 1001.6(c). It was enacted by Stats. 1979, c. 913, p. 3141, 1, last amended by Stats. 1993, c. 221, 1, and repealed in 1995, repeal effective Jan. 1, 1996.

Matter of EAG, 24 I. & N. Dec. 591 (BIA Jul. 30, 2008) (respondent failed to establish that he was a member of a particular social group of "persons resistant to gang membership," as the evidence failed to establish that members of
Honduran society, or even gang members themselves, would perceive those
opposed to gang membership as members of a social group).
http://www.usdoj.gov/eoir/vll/intdec/vol24/3618.pdf

Matter of SEG, 24 I. & N. Dec. 579 (BIA Jul. 30, 2008) (neither Salvadoran youth who have been subjected to recruitment efforts by the MS-13 gang and who have rejected or resisted membership in the gang based on their own personal, moral, and religious opposition to the gang's values and activities nor their family members constitute a "particular social group.").
http://www.usdoj.gov/eoir/vll/intdec/vol24/3617.pdf

Casas-Castrillion is DETENTION. ACLU Practice Advisory on Casas-Castrillion v. DHS, 535 F.3d 942 (9th Cir. 2008).



http://lawprofessors.typepad.com/immigration/files/practice_advisory_cas...

Paredes v. Attorney General of U.S., 528 F.3d 196 (3d Cir. Jun. 9, 2008) (noncitizen must exhaust claim before BIA before raising it on petition for review), citing 8 U.S.C. 1252(d)(1) (exhaustion of administrative remedies mandatory and jurisdictional); see also Bonhometre v. Gonzales, 414 F.3d 442, 447 (3d Cir.2005) ("To exhaust a claim before the agency, an applicant must first raise the issue before the BIA or IJ, so as to give it the opportunity to resolve a controversy or correct its own errors before judicial intervention." (internal quotations and citation omitted)).

Perez Pimentel v. Mukasey, 530 F.3d 321 (5th Cir. Jun. 4, 2008) (Attorney General's promulgation of 8 C.F.R. 212.7(d) [the Attorney General generally "will not favorably exercise discretion ... with respect to immigrant aliens who are inadmissible ... in cases involving violent or dangerous crimes, except in extraordinary circumstances, such as those ... cases in which an alien clearly demonstrates that the denial of [relief] would result in exceptional and extremely unusual hardship."] not an ultra vires amendment of 8 U.S.C. 1182(h)(1)(B)), citing Mejia v.

Perez Pimentel v. Mukasey, 530 F.3d 321 (5th Cir. Jun.4, 2008) (8 C.F.R. 212.7(d) - creating enhanced hardship standard for violent or dangerous crimes - is not impermissibly retroactive because it does not completely foreclose relief and "neither attaches a new disability to past conduct nor upsets settled expectations."), citing Mejia v. Gonzales, 499 F.3d 991, 998 (9th Cir. 2007) (rejecting retroactivity challenge to 8 C.F.R. 212.7(d)).

United States v. Cepeda-Rios, 530 F.3d 333, 335 and n.9 (5th Cir. Jun.4, 2008) (an alternative holding is binding precedent), citing Pruitt v. Levi Strauss & Co., 932 F.2d 458, 465 (5th Cir. 1991) ("This circuit follows the rule that alternative holdings are binding precedent and not obiter dictum."), abrogated on other grounds by Floors Unlimited, Inc., v. Fieldcrest Cannon, Inc., 55 F.3d 181, 185-86 (5th Cir. 1995); McLellan v. Miss. Power & Light Co., 545 F.2d 919, 925 n.21 (5th Cir.