President Trump’s plan for a deportation force is meeting resistance in the courts, but Texas is about to pass a bill that will make all of the state’s law enforcement part of it—whether they like it or not.

Seven years after Arizona passed SB1070, Texas is on the verge of passing a similar bill that would give every police officer in the state the power to say “show me your papers.” The bill, SB4, demands that local police hold people for immigration agents and permits them to investigate a person’s immigration status upon arrest. If you plan on traveling to Texas, you may want to plan for spending a few extra days there—in jail.

In March, Texas Governor Greg Abbott said that he was willing to throw law enforcement leaders in prison if they didn’t spend their resources on immigration enforcement. Talking specifically about Travis County (i.e., Austin) Sheriff Sally Hernandez, Abbott said that Texas would pass legislation “that will impose criminal penalties where the sheriff herself can wind up behind bars, and hence be removed from office, fines that could add up to millions of dollars per year, as well as other penalties. We’re gonna make it so costly, so expensive, there’s no way that any city or county can take on sanctuary city policies.”

What is a sanctuary city, exactly? It depends on who you ask. As one popular narrative goes, sanctuary cities are helping immigrants who have committed crimes evade federal agents, and may be violating federal law themselves. Right-wing author Michelle Malkin suggested rebranding them “outlaw cities.”

This is, of course, nonsense. The Department of Justice has gradually slid toward a definition of sanctuary cities as those that violate a specific federal law, 8 U.S.C. Section 1373, which prevents local and state governments from having policies that prohibit sharing information about a person’s immigration status with federal immigration agents. Few, if any, localities are violating this law, meaning that sanctuary cities are rare, or entirely mythical. However, more often when people talk about sanctuary cities, they are talking about local law enforcement agencies that require a warrant signed by a judge before holding people in their custody for federal immigration agents. This is what Texas is on the verge of outlawing.

Why would a local law enforcement agency have such a policy? Because for many years, ICE would essentially ask local police to do them an unconstitutional favor: hold a person up to 48 hours (maybe more, over weekends and holidays), without probable cause, until ICE agents were able to pick them up. This favor is usually called a detainer request. In recent years, multiple federal courts have determined that local police (PDF), in the course of doing ICE that favor, had violated people’s Fourth Amendment rights. Government data show that 834 U.S. citizens and 28,489 legal permanent residents had detainers placed on them between 2008 and 2012. When a local law enforcement agency agrees to hold a person, it assumes liability, which some departments have learned the hard way: paying thousands in damages and other costs from lawsuits. Lehigh County, Pennsylvania, paid $95,000 in damages and attorneys’ fees for holding Ernesto Galarza, a U.S. citizen born in New Jersey, based on a detainer request from ICE.

Fulfilling a detainer request is entirely voluntary—the form ICE uses (PDF), even under Trump, still says “request” on it. Anything different would violate Tenth Amendment protections against commandeering by the federal government. So, it’s actually not “sanctuary cities” that are violating the law—in fact, law enforcement agencies with these policies are doing right by their residents by taking a step to avoid violating their constitutional rights. As the constitutional problems surrounding detainers became clear, more and more local sheriffs and police departments decided that doing ICE a favor wasn’t worth the time and expense. According to the National Sheriffs’ Association, which would like ICE to provide a judicial warrant alongside detainers, a majority of the nation’s sheriffs have a policy to demand more than ICE’s say-so before agreeing to hold someone.

For local law enforcement in Texas, deciding what’s best for your community—and budget—is about to become a Class A misdemeanor under SB4. The Texas Majors Cities Chiefs, Texas Police Chiefs Association, and sheriffs from the state’s largest cities, oppose the bill. It was always the case that Trump was going to need local law enforcement to build a deportation force. Where they wouldn’t sign up willingly, the administration sought to bully them with threats to their funding and a weekly report shaming them for refusing to honor detainers. With the funding threats blocked by a federal court, Trump may have to rely on governors like Abbott to force local law enforcement’s hand.

Trump inherited a constitutionally flawed immigration enforcement system from his predecessor. Demanding compliance with that system—by either states or the federal government—threatens the safety and rights of us all. If passed, SB4 will almost certainly lead to frequent and systematic violation of people’s constitutional rights, regardless of one’s immigration or citizenship status. Texas may get a few laudatory presidential tweets for passing SB4, but everyone in Texas will soon come to regret it.