Clarence Thomas' constitutional argument against federal gun law gets first major court test

A convicted heroin trafficker's appeal could upend one of the federal government's most-used gun laws after a federal appeals court agreed to reconsider its constitutional foundation, weeks after Justice Clarence Thomas urged lower courts to take a fresh look at whether Congress had the authority to enact it.

The full Fifth Circuit Court of Appeals voted Monday to rehear United States v. Squire, a case that could determine whether Congress exceeded its constitutional authority when it enacted...