Texas Gov. Greg Abbott speaks during a news conference at the state Capitol on June 8, 2021, in Austin, Texas.
CNN  — 

Texas Republican Gov. Greg Abbott kicked his war against the Biden administration’s immigration policies up a notch with an executive order Wednesday targeting the transportation of migrants released from custody.

The order is framed as a public health measure to address Covid-19, which is surging in Texas amid Abbott’s opposition to new mask mandates or requirements for vaccines. It’s also prompted the threat of a lawsuit from US Attorney General Merrick Garland.

Here is what you need to know about the executive order, its potential impact on the ground and the possibility of legal battle:

What does the order say?

Abbott’s order says he’s directing Texas state troopers – under the Department of Public Safety – to stop any vehicle if there is “reasonable suspicion” that it is transporting certain migrants who illegally crossed the US-Mexico border and were released from the custody of US Customs and Border Protection.

If the state officials confirm that migrants being transported fit that category, the agency then must reroute the vehicle to its point of origin, according to the order. The order also gives state troopers the authority to impound vehicles being used to transport the migrants in question.

Why did Abbott issue it?

In his news release announcing the order, Abbott claimed that the rise in Covid cases in Texas is connected to the “dramatic rise in unlawful border crossings.” It is true that Texas has seen some of the highest Covid case increases in the country, but the role that border crossings have played in that surge is uncertain, at best. Instead, public health officials have blamed Texas’ recent rise in cases on the state’s lower vaccination rates.

Abbott’s critics say the Covid rationale for the migrant transport is hypocritical, as he has vehemently opposed other Covid public health policies, including the Biden administration effort to fund testing for immigrants released from custody.

What is well established is that Abbott has been on a warpath against key Biden immigration policies, including the administration’s willingness to release border crossers into the United States who have been picked up by federal immigration officials.

A bus station in McAllen has become a flashpoint in the tension between Texas Republicans and the Biden administration. Once immigrants caught illegally crossing the border have been processed by federal authorities, Customs and Border Protection officials have dropped them off at the station. From there, other private entities – including religious organizations contracting with the federal government – have arranged transport for the immigrants. Abbott’s order exempts federal, state or local authorities in his prohibition on transporting the migrants in question.

“The result would be to strand a whole bunch of undocumented immigrants at bus stations,” said Stephen Vladeck, a CNN contributor who’s a law professor at the University of Texas Law School. “Abbott’s not proposing that the state is going to hold them. Abbott can’t force the federal government to hold them. So instead he is just going to make it harder for the federal government to execute the policy choices it has made.”

But the Biden administration hasn’t taken all of these moves lying down, and Wednesday’s order quickly earned a warning shot from the administration, in the form of a Justice Department letter Thursday threatening a lawsuit. Abbott responded that he would fight any effort from the Justice Department.

Abbott’s critics are already questioning the legality of the order. There are two main areas where it could be vulnerable to legal challenge, according to Vladeck. It could be deemed an illegal preemption of a federal contract, since bus companies are often transporting migrants as part of work for the federal government.

And it also may run afoul of the Supreme Court’s decision in the 2012 case Arizona v. United States. In that case, the Obama administration challenged an Arizona law that empowered state officials to arrest individuals suspected of being undocumented immigrants. The court upheld some aspects of the Arizona law but struck down others that trampled on the federal government’s “broad, un-doubted power over the subject of immigration.”

The Abbott order is in “some ways worse” than the Arizona law, according to Thomas Saenz, the president and general counsel of MALDEF, an immigrant rights organization, as the Arizona law at least sought to have local authorities enforce immigration law as part of their duties to enforce state laws.

“This says go out and affirmatively pull someone over for what is an immigration-related issue,” Saenz said.

Saenz also compared the order to the legal troubles that former Maricopa County Sheriff Joe Arpaio ran into for targeting immigrants in traffic stops. His policing practices were ruled unconstitutional racial profiling by a federal court, and he was later convicted of criminal contempt for his refusal to stop them. (Trump pardoned Arpaio in 2017).

By framing his order around the Department of Public Safety’s authority to police motor vehicle traffic and by aiming the order at vehicles suspected to be leaving places where Customs and Border Protection releases immigrants, Abbott may have been searching for some wiggle room around those cases.

Abbott’s office did not respond to CNN inquiries about the legal questions around the order.

How will it be enforced?

There are questions about how eager the Department of Public Safety will be to implement the order. Kathleen Campbell Walker, a former president of the American Immigration Lawyers Association, wondered how the department would even train its officers in enforcing it. Walker was hired by El Paso County in 2006 to train its deputies on how to comply with the law while engaged in traffic stops with individuals whom they suspected lacked immigration status.

“So I have to figure out what factors would I be looking for to stop a vehicle because there appear to be people in it who would be subject to expulsion under the Title 42 order,” she said, referring to the Trump-era policy linked to the coronavirus pandemic that allows border authorities to swiftly expel migrants encountered at the border. “In my opinion, it creates a potential impossibility of performance situation for law enforcement.”

In a statement, the Department of Public Safety was vague about its plan to enforce the order.

“The Texas Department of Public Safety (DPS) is committed to securing our border under the direction of Governor Greg Abbott and through the Executive Orders applicable to DPS,” it said. “While the department does not discuss operational specifics, we will continue to monitor the situation at the border to make real-time decisions and adjust operations as necessary.”

Regardless, the order puts those who transport migrants – including entities that contract with the federal government – in an uncomfortable spot, as it prohibits that transport and exposes those organizations to the possibility that their vehicles will be impounded.

“There’s a fear that humanitarian volunteers could end up having their vehicles seized because they were taking a migrant to the bus station,” Aaron Reichlin-Melnick, policy counsel at the American Immigration Council, told CNN.

The reaction to the order from Greyhound – the bus company often used by the government’s private partners to transport immigrants – was terse: “Greyhound complies with all federal and state laws,” the company said in a statement.

CNN’s Priscilla Alvarez contributed to this report.