The US government is set to give Congress a bill allowing it to buy more than 2.5 million guns that were made before the 1968 federal assault weapons ban.
But the National Shooting Sports Foundation says the ban is unconstitutional, and the US Attorney General says the move violates the constitution.
The National Rifle Association and the American Civil Liberties Union have called the move “dangerous and unprecedented.”
Lawmakers in the House of Representatives and Senate will vote on the bill on Thursday.
If passed, it would set up a special panel to review the law, which expired on June 30.
Under the law that expired in June, the government can sell any guns made after the ban ended if they were purchased with cash or other financial support from a federally licensed firearms dealer, as long as they were “made in the United States.”
The bill would also allow the government to buy the guns if they are made in other countries.
The bill would give Congress 30 days to write a new law to address the legal and ethical issues around the transfer of weapons that were previously banned.
The law has been challenged in court.
A federal judge struck down parts of the ban on gun manufacturers in January, ruling the law was unconstitutional because it violates the Second Amendment rights of citizens.