President Donald Trump has taken significant steps to limit union rights for many federal workers through a new executive order. The Office of Personnel Management (OPM) announced Thursday that Trump’s order instructs numerous government agencies to terminate their collective bargaining agreements and cease union negotiations, potentially stripping hundreds of thousands of federal employees of union representation.

A White House fact sheet accompanying the order states that the Civil Service Reform Act of 1978, which allowed government workers to unionize, “enables hostile Federal unions to obstruct agency management.”

The administration is invoking an arcane provision in the Civil Service Reform Act claiming that collective bargaining rights can be terminated in instances where unions pose a national security threat. The administration’s sudden reliance on this never-before-used rule — coming at the crescendo of open conflict with federal employee unions — suggests the national security justification is merely a convenient pretext for a strong-arm tactic in a broader power struggle against the federal workforce.