Texas lawmakers in 2023 approved Senate Bill 4, which allows Texas police to arrest people for illegally crossing the Mexico border into Texas. It was expected to go into effect in early March, but legal challenges from the U.S. Justice Department and immigration advocacy organizations have repeatedly prevented the law from going into effect as litigation makes its way through federal courts. A federal appeals court this year once again blocked the state of Texas from enforcing the law—hours after the U.S. The Supreme Court had allowed the law to go into effect while the federal court case continued.

The Senate 4 bill is a new law that would make it a state crime to cross the Texas-Mexico border between ports of entry. If a police officer believes they have evidence that a person illegally crossed the Rio Grande, that person could be charged with a Class B misdemeanor, which carries a punishment of up to six months in jail. For subsequent offenses, the person could be charged with a second-degree felony and face up to 20 years in prison. If the migrant is convicted and has served their sentence, a judge would be required to order police to transport them to a port of entry. A judge could drop the charges if a migrant agrees to return to Mexico, and police could turn over migrant families to Border Patrol agents to avoid separating children from their parents instead of arresting them.

A federal appeals court order has blocked the law ahead of a scheduled hearing in the lawsuit brought forward by immigrant rights advocates and the federal government. This came hours after the U.S. Supreme Court on March 19 an order issued allowing the state of Texas to enforce SB 4 as challenges to the law proceed in federal court. Just one day before, the high court had extended a temporary court order blocking the law from going into effect.

This law is being challenged because immigration advocacy organizations and the Department of Justice say the law encroaches on the federal government’s sole authority over immigration and will lead to racial profiling by police. Texas officials have argued the state needs to step in because the federal government isn’t doing enough to stop illegal immigration.