A group of employees tasked with carrying out a controversial new immigration policy under the Trump administration is backing a lawsuit to end the practice, drawing the ire of a new Trump appointee to lead that workforce.

An American Federation of Government Employees council that represents some of the asylum officers posted a brief this week in support of blocking the Trump administration from sending asylum seekers to Mexico as they await immigration proceedings. Ken Cuccinelli, whose own appointment last month to head U.S. Citizenship and Immigration Services was not without controversy, quickly fired back at the employees for “choosing to deny reality.”

The union represents 2,500 employees at USCIS in the Washington, D.C., area and at overseas offices, including in Mexico. Some of those employees handle asylum claims and have been responsible for implementing the administration’s Migrant Protection Protocols, colloquially known as “remain in Mexico.” The policy requires individuals entering the United States to be returned to Mexico, regardless of their country of origin, while they wait for a hearing from an immigration judge.

A federal judge in April blocked the Trump administration from carrying out the policy, but a higher panel of judges allowed it to continue while the injunction is being appealed.

In an amicus curiae filed with the plaintiffs on the appeal, the AFGE council said its members have “first-hand knowledge” as to whether the protocols are in compliance with federal and international laws. The group argued the policy violates the government’s obligation to protect those seeking asylum from persecution, as it is returns a “vulnerable population” to a “hostile territory” in Mexico.

The policy places too many restrictions on asylum officers to reasonably determine if migrants are at risk of persecution if returned to Mexico, the union said. The protocols force its members to violate domestic law and international treaties, the group added, “something they did not sign up for when they decided to become asylum and refugee officers for the U.S. government.”

“Asylum officers are duty bound to protect vulnerable asylum seekers from persecution,” the union wrote. “However, under the [Migrant Protection Protocols], they face a conflict between the directives of their departmental leaders to follow the [protocols] and adherence to our nation’s legal commitment to not returning the persecuted to a territory where they will face persecution.”

Additionally, the union said, the protocols are “entirely unnecessary” as its members and the immigration system are nimble enough to handle the flow of migrants through the southern border. The policy adds to an already strained system by blocking the expedited removal of those without a “credible fear” of persecution and diverting asylum officers from their normal tasks. An influx of asylum officers and immigration judges, the group argued, would better remedy the problem.

“The [new policy], contrary to the administration’s claim, does nothing to streamline the process, but instead increases the burdens on our immigration courts and makes the system more inefficient,” the union wrote.

Cuccinelli said the union’s brief demonstrated “the complaining union leaders are choosing to deny reality.”

“Our system is broken,” Cuccinelli said in a tweet. “Even Democrats now admit we are in a crisis. But not the union…” He added the administration is taking action while “the union plays games in court” in order to “score short-term political points.”

The recent dustup follows a previous spat between the acting USCIS director and his employees. Cuccinelli sent an email last week indicating asylum officers were advancing too many asylum seekers from their credible fear interviews to proceedings in immigration court. Michael Knowles, president of the AFGE counsel that filed the court brief, took the email as “pressuring employees to misapply laws.”

“These dedicated civil servants are, indeed, upholding the Constitution and the law—and they should never be pressured to do otherwise,” he said. “These asylum officers deserve the respect and gratitude of the country they so proudly serve.”

Danielle Spooner, president of another AFGE council that represents 13,000 USCIS employees, was even more blunt in her condemnation of Cuccinelli’s message.

"To thrust blame for the influx and backlog of asylum seekers on our hard-working asylum officers who proudly serve their country in adjudicating asylum claims is despicable," Spooner said.