(WASHINGTON, D.C.) — The Supreme Court agreed on Monday to take up a Biden administration appeal over the regulation of difficult-to-trace ghost guns that had been struck down by lower courts. The justices by a 5-4 vote had previously intervened to keep the regulation in effect during the legal fight. Ghost guns, which lack serial numbers, have been turning up at crime scenes with increasing regularity. [time-brightcove not-tgx=”true”] The regulation, which took effect in 2022, changed the definition of a firearm under federal law to include unfinished parts, like the frame of a handgun or the receiver of a long gun, so they can be tracked more easily.