In the case of Rehaif v. United States, the Supreme Court ruled that in order for someone to be convicted under federal law as an illegal alien in possession of a firearm, prosecutors must prove that the defendant knew they were illegally or unlawfully in the country. Hamid Mohamed Ahmed Ali Rehaif, a citizen of the United Arab Emirates who was studying at Florida Institute of Technology on a nonimmigrant student visa, was dismissed from his studies and subsequently remained in America beyond his authorized period. During this time he visited a firing range where he shot two firearms - an act which is prohibited by federal law for people who are illegally or unlawfully residing within U.S borders. He was charged with violating 18 U.S.C §922(g) but argued that government had failed to prove he knew about his unlawful status when engaging with firearms. The court agreed (7-2), stating it's not enough just to show defendants know they possessed guns; knowledge about their immigration status also matters.

In the dissenting opinion for REHAIF v. UNITED STATES, Justice Alito, joined by Justices Thomas and Kavanaugh, argued that the majority's decision was not supported by the text of 18 U.S.C. §922(g), which makes it unlawful for certain individuals to possess firearms. The dissenters contended that this law does not require knowledge of one’s prohibited status but only knowledge of possession of a firearm. They pointed out that Congress has shown in other statutes that it knows how to make status an element when it wants to do so and did not do so here. They also noted practical implications: thousands of convictions could be overturned due to this ruling because many defendants would claim they were unaware they fell into a category barring them from owning guns (e.g., convicted felons or illegal aliens). Lastly, they criticized the majority's reliance on legislative history as inconsistent with principles requiring clear statutory language before imposing severe penalties.