AUSTIN (Nexstar) — The Department of Justice announced Wednesday afternoon it filed a lawsuit against Texas over its contentious new border security law, accusing the state of infringing on federal authority and empowering local police to unconstitutionally arrest suspected illegal immigrants.

Last week, federal authorities threatened to sue to block Senate Bill 4 if Gov. Greg Abbott did not assure them the state will not enforce the law by Jan. 3.

According to the complaint filed in an Austin federal court, the feds argue, “Texas’s Senate Bill 4 (SB 4) creates purported state immigration crimes for unlawful entry and unlawful reentry, permits state judges and magistrates to order the removal of noncitizens from the country, and mandates that state officials carry out those removal orders. But Texas cannot run its own immigration system. Its efforts, through SB 4, intrude on the federal government’s exclusive authority to regulate the entry and removal of noncitizens, frustrate the United States’ immigration operations and proceedings, and interfere with U.S. foreign relations. SB 4 is invalid and must be enjoined.”

The four defendants named in the DOJ lawsuit are the state of Texas, Gov. Greg Abbott, the Texas Department of Public Safety and that agency’s director, Col. Steven McCraw.

Abbott signed the bill into law last month, telling Nexstar in a border bill signing ceremony in Brownsville that he believes the law is constitutional but would welcome a Supreme Court challenge to test the current balance of power over immigration law.

“Texas is prepared to take this fight all the way to the U.S. Supreme Court to protect Texans and Americans from President Biden’s open border policies,” Abbott’s communications director Renae Eze said. “President Biden’s deliberate and dangerous inaction at our southern border has left Texas to fend for itself.”

The looming legal battle comes as Congressional Republicans are forging a stark split-screen with the Biden administration on Wednesday. U.S. House Speaker Mike Johnson is making his first public trip of his tenure as speaker to Eagle Pass, leading more than 50 House Republicans to tour the border and meet with Texas law enforcement.

Eagle Pass has been the epicenter of the humanitarian crisis on the southern border — and the political crisis in the White House. Federal immigration authorities encountered more than 300,000 migrants in December, including more than 71,000 in the sector including Eagle Pass. Only 32% of Americans are confident in President Biden’s ability to make wise decisions on immigration policy, Pew Research Center reported in December.

Senate Bill 4 is set to go into effect in March unless a federal challenge puts it on pause.