Without intervention, the law would have gone into effect on the morning of March 10. The Justice Department said that 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.”

Senate Bill 4, signed into law by Texas Gov. Greg Abbott in December, immediately raised concerns among immigration advocates of increased racial profiling as well as detentions and attempted deportations by state authorities in Texas, where Latinos represent 40% of the population.

Last week, a federal judge in Austin, Texas, had blocked the state government from implementing the law.

“If allowed to proceed, SB 4 could open the door to each state passing its own version of immigration laws,” Judge David Alan Ezra wrote.

A federal appeals court over the weekend granted a temporary stay of the lower court’s decision and said the law would take effect later this week if the Supreme Court did not act.

This story and headline have been updated with additional developments.