In Lockhart v. United States (2015), the Supreme Court ruled on the interpretation of a federal law that imposes mandatory minimum sentences for certain repeat sex offenders. Avondale Lockhart was convicted in 2000 for sexual abuse involving his then-girlfriend's daughter and later, in 2008, he was found guilty of possessing child pornography. The issue at hand was whether his first conviction could be considered as a predicate offense under federal law to impose an enhanced sentence for his second conviction. The statute specifies that mandatory minimums apply if the defendant has prior convictions "relating to aggravated sexual abuse, sexual abuse or abusive sexual conduct involving a minor or ward". In an unusual split decision, Justice Sonia Sotomayor wrote the majority opinion stating that because Mr.Lockhart’s previous crime involved an adult and not a minor it did not qualify him for increased sentencing under this specific provision.

In the dissenting opinion for Lockhart v. United States, Justice Sonia Sotomayor argued that the majority's interpretation of 18 U.S.C §2252(b)(2) was incorrect and inconsistent with Congress' intent. She contended that the law should only apply to those who have prior state convictions related to child pornography or sexual abuse involving minors, not any type of sexual offense as interpreted by the majority. According to her, this broader interpretation could lead to harsher penalties for individuals whose previous offenses were unrelated to child exploitation or pornography. Furthermore, she pointed out inconsistencies in how similar laws are applied across different jurisdictions due to varying definitions of "sexual abuse". Lastly, she criticized the majority’s reliance on a grammatical rule known as “the last-antecedent canon” which they used in their statutory interpretation.