The Congress has over the years surrendered so much of its authority to check and balance presidents and their cabinet picks that it is perhaps unsurprising that some commentators were taken aback when Congressional Progressive Caucus cochair Mark Pocan got serious about holding the Trump administration and its appointed henchmen to account for obstructing the impeachment inquiry.

Pocan’s response was certainly bold. After someone at the State Department—presumably Secretary of State Mike Pompeo—blocked congressional testimony by a key witness to the president’s scheming to strong-arm the Ukrainian government into investigating former vice president Joe Biden, Pocan pushed back with a proposal to withhold the salary of the obstructionist. Or obstructionists.

That’s a blunt response, but not an unreasonable one. It’s rooted in respect for the system of checks and balances as it was originally outlined in the Constitution.

The system only works when the branches of government cooperate with one another. And, this week, the executive branch refused to cooperate.

European Union Ambassador Gordon Sondland, a Trump campaign donor who was awarded an ambassadorship not because of his competence but because he wrote big checks, was supposed to provide testimony last week to the House Intelligence Committee. That testimony was blocked at the last minute as part of what was portrayed as a move by the administration to “declare war” on the impeachment inquiry. That sparked an immediate outcry over White House and State Department obstruction of the inquiry, and this outcry will only get louder following Friday’s testimony by former US ambassador to Ukraine Maria Yovanovitch that she was removed from her position because of pressure Trump placed on the State Department.

Sondland has indicated that he wants to testify next week. But the prospect that Pompeo and the Trump cabal within the State Department may continue their stonewalling is real. It demands a real response. And Pocan is providing it.

The Wisconsin Democrat wrote to Pompeo last Tuesday, demanding details about the blocking of Sondland’s testimony. But Pocan’s was not a typical “strongly worded letter.” It packed a punch. Referring to “section 713 of Division D of Public Law 116-6 signed by the President earlier this year,” the representative explained that “As you are aware, this section prohibits paying the salary of any ‘officer or employee of the Federal Government who prohibits or prevents…any other officer or employee of the Federal Government from…communication or contact with any Member, committee, or subcommittee of the Congress.’”

“I believe,” added Pocan, “[that] the person prohibiting Ambassador Sondland from testifying before the House Intelligence Committee is in violation of this statute, and that their salary should be withheld until Ambassador Sondland appears before Congress.”

As Pompeo is in charge of the State Department, and as he is notoriously “hands-on” when it comes to doing the president’s bidding, the salary in question is undoubtedly his. Yet the representative is not interested in personalities. He is interested in making two points.

First: “We refuse to bankroll this administration while they hold witnesses hostage,” says Pocan.

Second: Pocan has long recognized that Congress needs to get more serious about utilizing all of its powers to provide oversight and checks and balances. And he knows that the power of the purse is one of those powers. Along with the authority to declare (or block) wars and to impeach presidents, the Congress’s authority to authorize or refuse the spending of public dollars is an essential check and balance on the executive branch. James Madison referred to it as “the most complete and effectual weapon with which any constitution can arm the immediate representatives of the people, for obtaining a redress of every grievance.”

Pocan is asserting that power and his willingness to do so—along with this long-overdue impeachment inquiry—suggests that Congress might finally be prepared to reclaim its authority as a coequal branch of government.