A coalition of conservative-leaning states is making a last-ditch effort to keep in place a Trump-era public health rule that allows many asylum seekers to be turned away at the southern U.S. border.

Late Monday, the 15 states filed what’s known as a motion to intervene — meaning they want to become part of the legal proceedings surrounding the public health rule referred to as Title 42.

The rule, first invoked by Trump in 2020, uses emergency public health authority to allow the United States to keep migrants from seeking asylum at the border, based on the need to help prevent the spread of COVID-19.

It’s set to end Dec. 21, potentially upending border enforcement as Republicans are about to take control of the House from the Democrats following midterm elections and are planning to make immigration a central part of their agenda.

The states argued that they will suffer “irreparable harm from the impending Termination of Title 42” and that they should be allowed to argue their position well before the Dec. 21 termination date.

In a statement, a lawyer for the American Civil Liberties Union which has been arguing to end the use of Title 42 called into question the states’ motivation for trying to keep the public health rule in force.