United States v. Polk, 61 F.4th 1277

Conner Lee Polk, an enrolled Indian, drove intoxicated on an Oklahoma Indian reservation and collided with two cars, seriously injuring occupants in one vehicle.
Because no specific federal statute applied, the government prosecuted Polk under the Assimilative Crimes Act (ACA), which makes certain state crimes committed on federal enclaves (including Indian country via § 1152) federal offenses by assimilating state law.
Polk pleaded guilty to an Oklahoma DUI offense assimilated under the ACA that carries a state-prescribed mandatory sentence of 4–20 years (minimum 4 years); he received a separate concurrent six-month sentence for a property-damage offense.
At sentencing Polk asked for below‑minimum imprisonment relying on Oklahoma’s “safety‑valve” statute (Okla. Stat. tit. 22, § 985.1), which permits departures from state mandatory minimums in a broader set of circumstances than federal law allows.
The district court refused to apply the Oklahoma safety‑valve, concluding it conflicted with federal sentencing law—specifically 18 U.S.C. § 3553(e)–(f), which authorizes departures from federal mandatory minimums only for substantial assistance or certain enumerated drug offenders—and imposed the four‑year minimum.
The Tenth Circuit affirmed, holding the ACA requires only a "like" punishment and that federal sentencing policy controls where state law conflicts with Congress’s specific penal directives.

Issue	Polk's Argument	Government's Argument	Held
Whether a federal court sentencing under the ACA must apply Oklahoma’s safety‑valve to allow a sentence below the state mandatory minimum	Polk: District court should have applied Oklahoma § 985.1 and considered a sentence below 4 years	Gov: ACA requires only "like punishment" and federal sentencing controls; state safety‑valve conflicts with federal law	Court: No — ACA requires like, not identical, punishment; court need not adopt state departure rules that conflict with federal policy
Whether Oklahoma’s safety‑valve conflicts with federal sentencing law (18 U.S.C. § 3553(e)–(f))	Polk: § 3553(f) does not expressly exclude ACA offenses; no conflict	Gov: Oklahoma’s safety‑valve permits departures for broader reasons than § 3553(e)–(f), creating a direct conflict	Court: Yes — state law allows departures in circumstances beyond the exclusively enumerated federal exceptions, so federal law precludes applying the state safety‑valve
Whether ambiguity or legislative history/lenity alters the result	Polk: If statute ambiguous, legislative history and rule of lenity favor him	Gov: Statutory language is clear; those canons irrelevant	Court: Language unambiguous; did not reach legislative history or lenity arguments

United States v. Garcia, 893 F.2d 250 (10th Cir. 1989) (explains ACA jurisdiction for crimes on reservations)
United States v. Christie, 717 F.3d 1156 (10th Cir. 2013) (ACA requires a "like punishment," not identical state sentencing rules)
United States v. Jones, 921 F.3d 932 (10th Cir. 2019) (discusses when ACA fills gaps in federal criminal law)
United States v. Martinez, 1 F.4th 788 (10th Cir. 2021) (assimilated state offense becomes a federal offense punishable under federal law)
United States v. Wood, 386 F.3d 961 (10th Cir. 2004) (federal courts decline to assimilate state sentencing laws that conflict with federal Guidelines/policy)
United States v. Chapman, 839 F.3d 1232 (10th Cir. 2016) (standard of review for legal sentencing questions)