Men stand in a McAllen Border Patrol station on July 12, where hundreds of men were kept in caged fences with no cots amid sweltering heat. Photo: Josh Dawsey/The Washington Post via AP

Sixteen asylum seekers who alleged the federal government treated them inhumanely in Texas immigration detention centers are preparing to go before a federal judge Thursday and Friday to argue for a preliminary injunction.

If the migrant men win a preliminary injunction, it would mean that in four South Texas counties, U.S. Customs and Border Patrol would have to give detainees access to lawyers and either drastically improve conditions in short-term immigration detention facilities known as "hieleras" or iceboxes, or stop keeping people there longer than 72 hours.

"It would be a big development for the region. It would also put other sectors of the border patrol on notice that they can't treat detainees in an unconstitutional fashion and hide behind a claim that these are designed for short-term use when detainees in our case have been detained weeks or months," said Haynes and Boone associate Brent Beckert, who represents the plaintiffs pro bono.

Haynes and Boone counsel Luis Campos added, "There are legal mechanisms for transfer to ICE, or release under parole or release pursuant to bond or release with an ankle monitor."

The plaintiffs' 67-page motion for preliminary injunction in Rivera Rosa v. McAleenan details the conditions migrants face in Customs and Border Patrol custody. They sleep standing up, packed side-by-side in small cells. They are fed only bologna sandwiches, leading to constipation. There are jugs of highly chlorinated water that is too smelly to drink, and migrants must share cups.

The motion claims the temperature is between 64 to 67 degrees, and officers confiscate detainees' clothes and fail to provide new clothing, leaving people—even infants—shivering. No one can wash laundry, wash their hands, shower, or even have steady access to toilets. People get sick frequently, according to the motion.

A team of Haynes and Boone pro bono attorneys and counsel from the Texas Civil Rights Project, Refugio Del Rio Grande and individual lawyers represent the migrant men. Seeking to represent a class of asylum seekers, they ultimately hope for habeas corpus relief to gain release from what they allege are deplorable conditions in U.S. Customs and Border Patrol facilities in the Rio Grande Valley, said their second amended petition. The plaintiffs also alleged a lack of access to any attorneys and improprieties in how the government interviews asylum seekers to determine if they're eligible for asylum.

"It causes some detainees to become so desperate that they relinquish their legal rights and accept removal, simply to escape the unbearable conditions," their petition said.

The defendants are U.S. Department of Homeland Security Acting Secretary Kevin McAleenan, Customs and Border Patrol Acting Commissioner John Sanders, U.S. Border Patrol Chief Carla Provost and Rio Grande Valley Chief Patrol Agent Rodolfo Karisch, and Michael Pitts, field office director of the Port Isabel Detention Center.

The defendants countered in an Aug. 26 response to the motion for a preliminary injunction that the plaintiffs came into the U.S. during a surge of immigration, when Customs and Border Patrol facilities were overcrowded. The plaintiffs now are out of detention, said the response. The government argued that the court doesn't have jurisdiction over their claims, which face statutory bars.

Also, conditions and detention times have improved substantially since the plaintiffs sued: One new Customs and Border Patrol facility has showers, laundry, meals, sleeping mats and free phone calls, among other improved conditions, the response said.

Their attorneys, Assistant U.S. Attorney Christopher Pineda of the Southern District of Texas and Michael Anthony Celone of the U.S. Department of Justice Civil Division, didn't immediately respond to a request for comment.

Read the motion for preliminary injunction: