The U.S. Constitution’s “double jeopardy clause” prohibits the prosecution of a defendant twice for the same crime. But, state and federal governments often prosecute a person for the same underlying crime under their own laws. In a case that may greatly impact criminal appeals and prosecutions, the U.S. Supreme Court heard argument earlier this month on whether a person can be charged with the same crime under federal and state laws.

The case is an appeal of a defendant who was stopped by police in Alabama for a broken tailgate in 2015. Marijuana and a firearm were found in his vehicle. Possession of the gun was a criminal offense because of his earlier felony conviction for second-degree robbery.

He was convicted for gun possession by the State of Alabama and he served a year in state prison. The federal government, however, also filed criminal charges for the gun possession. He was convicted of the federal offense and is serving time in a federal high-security facility in Texas. His release date is scheduled for February of 2020.

His attorneys argue that the dual prosecutions violate the Fifth Amendment’s prohibition on double jeopardy. Federal prosecutors, however, claim that the dual prosecutions are permitted under the separate sovereigns, which the Supreme Court has upheld in earlier decisions. This doctrine has been in use for over 150 years, according to the Congressional Research Service.

Federal law has grown drastically, which has increased the overlap between federal and state prosecutions. Many opponents of the dual sovereign doctrine claim that it harms criminal justice by incarcerating defendants twice for the same offense. Reversing this doctrine would not eliminate all dual prosecutions, according to an expert. Two offenses are not the same for double jeopardy purposes unless prosecution requires proof of the same facts.