A federal judge in Austin, Texas, ordered the state government Thursday to suspend enforcement of a controversial law that would allow state law enforcement agents to arrest and detain people they suspect of entering the country illegally.

“If allowed to procced, SB 4 could open the door to each state passing its own version of immigration laws,” Judge David Alan Ezra wrote, granting a preliminary injunction against the law.

The judge rejected the state’s argument that the current influx of migrants across the southern border is an “invasion” that Texas has the right to stop unilaterally. “SB 4 threatens the fundamental notion that the United States must regulate immigration with one voice,” Ezra wrote.

Without action from the court, the law was set to go into effect on Tuesday. Plaintiffs include the federal government and El Paso County, which claims enforcing the law would strain its jail system with thousands of new arrests.

“El Paso County applauds the court’s clear confirmation today that immigration policies rest solely under Federal jurisdiction, and the state of Texas’ interference with the U.S. Constitution will not be tolerated,” said Iliana Holguin, a commissioner for El Paso County.