The US Citizenship and Immigration Services employees union said that an email sent by the agency’s leader threatening to fire anyone for leaking information to the media was an illegal attempt to intimidate whistleblowers, according to a copy of a letter the union sent to Department of Homeland Security officials on Tuesday.

The acting leader of USCIS, Mark Koumans, sent the email to employees last week, telling them that as they regularly handle sensitive information, they need to guard it closely.

Koumans also said that “recent unauthorized disclosures of sensitive, for official use only, and internal use only information by USCIS personnel to media outlets have brought this issue to the forefront.”

He added that any staffer would be reprimanded and potentially suspended for two weeks for a first offense, another two weeks for a second offense, and terminated or removed from their job for a third leak.

The head of the union — which represents more than 13,000 USCIS workers — and the Government Accountability Project wrote to Koumans and the acting deputy director of DHS, Ken Cuccinelli, on Tuesday to raise their concerns with the language in the email.

The letter claimed that the directive from Koumans “was intended to illegally intimidate whistleblowers from lawfully reporting ongoing abuses by the Department of Homeland Security (DHS).”

Koumans’ email, the letter explained, did not contain the necessary language to inform USCIS employees of their whistleblower rights.

“That it is intended to chill employees from engaging in protected whistleblowing is demonstrated by the fact that the directive was issued just days after current and former USCIS employees publicly blew the whistle on significant misconduct, particularly concerning MPP — the Migrant Protection Protocols or ‘Remain in Mexico’ policy — as well as a new policy ordering the deportation of asylum seekers to Guatemala,” the letter stated.

The letter also pointed to an earlier claim by Cuccinelli, who was previously acting director of USCIS, that the agency had disciplined a number of “leakers.” BuzzFeed News requested details of the statement but did not receive a comment from USCIS.

“USCIS’ messages to employees in the form of illegal gags and threats seek to, and likely will impede, the exercise of their whistleblower rights,” said the letter. “Employees reading their agencies’ rules will not know they have the right to contact Congress or the media to expose misconduct. Even employees who know their rights may be intimidated from speaking out of fear of violating agency policy.”

Union officials are calling on USCIS to issue a corrected letter to the agency’s employees, better detailing their rights as whistleblowers.

The agency has been on the forefront of the Trump administration’s overhaul of the asylum system. In the past year alone, the administration has forced asylum-seekers to remain in Mexico for their cases to be heard in the US, barred asylum for those who crossed through Mexico, and, last Wednesday, began a program to deport those at the southern border seeking protection from Honduras and El Salvador to Guatemala.

USCIS officials, including asylum officers and others, have been pushed to administer all three controversial programs. BuzzFeed News first revealed the implementation of the program on Wednesday, Nov. 20. Later in the day, Reuters, which also reported the program starting up, posted training materials for asylum officers on the plan to deport individuals to Guatemala.

“We want to get the public’s attention on this, along with our representatives in Congress, in making sure that our agency follows the law,” said Michael Knowles, an asylum officer and spokesperson for the National CIS Council 119.