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.

“Make no mistake: S.B. 4 bypasses federal immigration authority and threatens the integrity of our nation’s constitution and laws,” a coalition of groups that sued over the law, including the American Civil Liberties Union, said in a statement.

Republican Gov. Greg Abbott signed the law in December as part of a series of escalating measures on the border that have tested the boundaries of how far a state can go to keep migrants from entering the country.

The law would allow state officers to arrest people suspected of entering the country illegally. People who are arrested could then agree to a Texas judge’s order to leave the country or face a misdemeanor charge for entering the U.S. illegally. Migrants who don’t leave after being ordered to do so could be arrested again and charged with a more serious felony.

The Justice Department told the Supreme Court that the law would profoundly alter “the status quo that has existed between the United States and the States in the context of immigration for almost 150 years.” It went on to argue that the law would have “significant and immediate adverse effects” on the country’s relationship with Mexico and “create chaos” in enforcing federal immigration laws in Texas.

The federal government cited a 2012 Supreme Court ruling on an Arizona law that would have allowed police to arrest people for federal immigration violations, often referred to by opponents as the “show me your papers” bill. The divided high court found that the impasse in Washington over immigration reform did not justify state intrusion.