Attorney General Merrick Garland on Thursday asked Texas Governor Greg Abbott to immediately revoke an executive order that instructs state authorities to stop vehicles suspected of carrying migrants released from U.S. Border Patrol custody, arguing that such a directive is illegal and unconstitutional. On Wednesday, Abbott, a Republican who has vocally opposed the Biden administration’s immigration policies, ordered the Texas Department of Public Safety to stop and re-route vehicles “upon reasonable suspicion” that they may be transporting migrants who crossed the southern border without authorization. Abbott said the order is designed to protect Texas communities from migrants who could spread the coronavirus, accusing the Biden administration of fueling a public health crisis along the borderlands by scaling back Trump-era restrictions. But Garland wrote in a letter to Abbott that Texas did not have the legal authority to issue such orders, asserting that the governor’s directive interfered with federal immigration enforcement and could jeopardize the health of migrants in U.S. government custody. “Among other harms, the Order would exacerbate and prolong overcrowding in facilities and shelters and obstruct the federal government’s arrangements with state, local, and non-governmental partners to ensure that released individuals are transported for appropriate COVID-19 testing to address public health concerns,” Garland wrote in his letter to Abbott. Garland vowed to pursue “legal remedies” if Abbott fails to rescind his order. Abbott’s directive exempted federal, state and local law enforcement, but Garland said it could affect government personnel who are not classified as law enforcement officials — such as staff transporting unaccompanied children — as well as contractors who work with the Biden administration. Advocates said the order could also affect border-area shelters and non-profits that assist asylum-seekers, as well as buses that transport migrants to their respective destinations in the U.S. In his order, Abbott asked state authorities to take vehicles to official border crossings if they confirmed migrants are on board. Garland said that would impede the government’s ability to release migrants and to ensure they comply with their immigration appointments. While the Biden administration has continued to use a public health authority invoked under President Donald Trump to expel border-crossers without asylum hearings, it exempted unaccompanied minors from the policy and has been allowing most families with children to stay in the country temporarily while they request U.S. refuge. Unaccompanied children are transferred to shelters and other housing sites overseen by the Department of Health and Human Services, while most families are released to local shelters or briefly held in hotels or government sites after being discharged from Border Patrol custody. Local advocates have been testing families for the coronavirus after their release from U.S. custody and quarantining some of them, including those who test positive for the virus. Most families leave the borderlands by plane or bus to reach their respective destinations across the U.S., where they are expected to attend court appointments. Wednesday’s directive is one of several border-related orders that Abbott has issued in recent months over his disagreements with the Biden administration. He has already instructed Texas law enforcement to arrest migrants who can be served with state trespassing charges and ordered state agencies to stop licensing shelters that house unaccompanied children in federal custody. Clare Hymes and Nicole Sganga contributed reporting.