Texas’ plans to arrest migrants who enter the U.S. illegally and order them to leave the country is headed to the Supreme Court in a legal showdown over the federal government’s authority over immigration.

An order issued Monday by Justice Samuel Alito puts the new Texas law on hold for at least next week while the high court considers what opponents have called the most dramatic attempt by a state to police immigration since an Arizona law more than a decade ago.

The law, known as Senate Bill 4, had been set to take effect Saturday under a decision by the conservative-leaning 5th U.S. Circuit Court of Appeals. Alito’s order pushed that date back until March 13 and came just hours after the Justice Department asked the Supreme Court to intervene.