House Democrats are threatening to force Trump administration officials’ compliance with their impeachment inquiry by targeting something they hold dear: their paychecks.

Democrats have twice referenced using an obscure provision in the annual Financial Services spending bill, referred to as Section 713, that says any federal employee who “prohibits or prevents, or attempts or threatens to prohibit or prevent” another official from communicating with lawmakers shouldn’t be paid during that time.

The process for carrying out such a threat is relatively simple. First, lawmakers request a Government Accountability Office investigation, after which the GAO would issue a legal opinion on whether administration officials have blocked certain federal employees from testifying or otherwise communicating with lawmakers or their aides.

If any wrongdoing is found, the GAO would inform the relevant agency and suggest it claw back salary paid during that time. The agency would then seek repayment from the offending federal employee — if timely payment wasn’t made, it could be sent to a collection agency.

The relatively unknown provision has rarely been used during its 22-year history, with at least two key exceptions.