Roughly one week after the Fifth Circuit U.S. Court of Appeals handed Texas a win on its border security law, SB 4, the law is facing a second legal challenge.

The American Civil Liberties Union, ACLU of Texas, and the Texas Civil Rights Project filed a class-action lawsuit on Monday seeking a temporary restraining order and preliminary injunction to block the law from going into effect.

The law, which makes illegal entry into Texas a state crime, is set to go into effect May 15. It gives Texas law enforcement the authority to return illegal foreign nationals to a port of entry and/or arrest them for unlawful entry, among other provisions.

After the bill was signed into law in 2023, multiple groups sued, arguing the law is unconstitutional. A district court and panel of Fifth Circuit judges agreed.

The full Fifth Circuit disagreed and reversed the lower court’s ruling – but solely on procedural grounds. The court held the plaintiffs didn’t have standing to sue, enabling a door to remain open challenging the law on its merits. As expected, another lawsuit was filed.

The class action lawsuit was filed in U.S. District Court for the Western District of Texas Austin Division and names the Texas Department of Public Safety and its director as defendants.

SB 4 “is one of the most extreme anti-immigrant laws ever passed by any state legislature in the country” and will “separate families and directly lead to racial profiling,” the ACLU argues.

It will also “transform our police and judges into immigration agents – threatening neighbors who have families here, who have lived here for years, even those who have legal status,” ACLU of Texas legal director Adriana Piñon said. “Immigration enforcement is exclusively the federal government's arena, and no state has ever claimed the power Texas threatens to wield here. We are taking this back to court to defend our Texas communities.”

The groups said they “seek to represent thousands of people across the state who may be held liable for violating the reentry provision” of SB 4. They currently represent a lawful permanent resident and visa holder they say would be impacted by the law if it were go to into effect.

“Every court to have reached the merits of laws like S.B. 4 has found them to be unconstitutional,” Cody Wofsy, deputy director of the ACLU’s Immigrants’ Rights Project, said. “The en banc Fifth Circuit did not reach the constitutional questions at the heart of this case: whether S.B. 4 violates the Supremacy Clause of the U.S. Constitution and unconstitutionally strips the federal government of its exclusive authority over immigration enforcement,” the ACLU added.

The lawsuit was filed as Texas DPS is implementing Gov. Greg Abbott’s border security plan, Operation Lone Star 2.0. Since Abbott launched OLS five years ago, from March 2021 through February 2026, OLS officers have apprehended 538,141 illegal foreign nationals, including those referred to Border Patrol. They’ve also deterred 157,112 illegal entries, according to OLS data obtained by The Center Square.

OLS officers have made 63,659 criminal arrests and 12,392 criminal trespass arrests. These include arrests of U.S. citizens and illegal border crossers.

Human smuggling arrests total 10,552 with 23,717 human smuggling charges reported, according to the data.

Total felony charges were 51,091 with 11,950 federal or other charges, with some arrests involving multiple felony charges, according to the data.

“OLS is more critical now than ever because we face more threats than we've ever faced before especially from Special Interest Aliens and suspected terrorists who are still coming across the border,” DPS Lt. Chris Olivarez told The Center Square. DPS troopers are arresting illegal foreign nationals with potential ties to terrorism, including Special Interest Aliens from Afghanistan, Egypt, the Congo, Mali, Pakistan, Syria, Turkey, Iran and other countries, The Center Square reported.

OLS officers are also targeting South American Theft Groups and criminal actors designated as foreign terrorist organizations like Tren de Aragua, among other violent criminals, The Center Square reported.

Abbott maintains the position he held several years ago as to why SB 4 is necessary. Former President Joe Biden’s "deliberate inaction … left Texas to fend for itself." He also maintains that Article 1 Section 10 of the U.S. Constitution empowers states "to take action to defend themselves and that is exactly what Texas is doing."

His press secretary, Andrew Mahaleris, told The Center Square, “Governor Abbott signed SB 4 into law to protect Texas and America from President Biden’s open border policies, the effects of which did not disappear overnight. Texas will not back down from its constitutional right to self-defense.”