In the case of Clifton Terrelle McNeill v. United States, 2010, the U.S. Supreme Court ruled that federal courts must use a defendant's state law at the time of conviction to determine whether prior convictions qualify for sentence enhancements under the Armed Career Criminal Act (ACCA). The ACCA imposes a mandatory minimum sentence on defendants convicted of being felons in possession of firearms if they have three or more previous convictions for serious drug offenses or violent felonies. McNeill had six prior felony convictions in North Carolina and was sentenced under ACCA after pleading guilty to possessing a firearm as a felon. He argued his past crimes were not punishable by over one year imprisonment because North Carolina laws changed since his sentencing reducing maximum sentences below ACCA’s threshold requirement. However, Justice Clarence Thomas delivered an unanimous opinion stating that current lenient state laws do not affect whether someone is subject to federal penalties based on older harsher versions of those same laws.

In the case of Clifton Terelle McNeill v. United States, there was no dissenting opinion recorded. The Supreme Court unanimously ruled that federal courts should use the maximum sentence under state law at the time of a defendant's conviction for determining whether prior convictions qualify as serious drug offenses under the Armed Career Criminal Act (ACCA). This decision affirmed that it is not relevant if state laws are modified to reduce penalties after an offender’s conviction when considering mandatory minimum sentences under ACCA.