The White House on Thursday formally published a controversial document that gives Defense Secretary Mark Esper the authority to end collective bargaining for the Pentagon’s nearly 750,000-person civilian workforce, more than three weeks after President Trump signed the memo.

The document, dated Jan. 29, which delegates Trump’s legal authority to exempt agencies from the law guaranteeing federal employees the right to unionize, is now available on the Federal Register.

In the memo, Trump argues that Esper may need to abolish unions from the Pentagon because of the need for “flexibility.”

“When new missions emerge or existing ones evolve, the Department of Defense requires maximum flexibility to respond to threats to carry out its mission of protecting the American people,” Trump wrote. “This flexibility requires that military and civilian leadership manage their organizations to cultivate a lethal, agile force adaptive to new technologies and posture changes. Where collective bargaining is incompatible with these organizations’ missions, the Department of Defense should not be forced to sacrifice its national security mission and, instead, seek relief through third parties and administrative fora.”

Although it is not yet clear how Esper might use his new authority, a 2017 White House memo advocated “eliminating employee unions” at the Defense Department as part of a multi-pronged effort to weaken organize labor. Several other ideas floated in that document have since made it into administration policy actions and proposals.

Since Government Executive first uncovered the existence of the memo earlier this month, it has drawn scorn from federal employee unions and bipartisan concern in Congress.

“Denying nearly half a million Defense Department workers the collective bargaining rights guaranteed to them by law since 1962 would be a travesty—and doing it under the guise of ‘national security’ would be a disgrace to the sacred oath and obligation that all federal workers make to their country," said Everett Kelley, national secretary-treasurer of the American Federation of Government Employees earlier this month. "This administration will not stop until it takes away all workers’ rights to form and join a union, and we will not stop doing everything we can to prevent that from happening.”

According to Federal News Network, Sen. Susan Collins, R-Maine, said she was “rigorously pursuing” inquiries into the matter at AFGE’s annual legislative conference last week.

“Think about the implications of that,” she told union members. “Left unchecked—and I’m determined to see that we overturn it—this decision could potentially affect hundreds of thousands of employees.”