A proposed Constitutional amendment that would allow Congress to invalidate presidential pardons secured its first Republican co-sponsor on Monday, marking an unusual moment of GOP resistance aimed at President Trump.

The effort comes as Trump’s use of the pardon power continues to spark bipartisan criticism. He began his second term by pardoning thousands of Jan. 6 defendants, including individuals accused of assaulting law enforcement during the 2021 Capitol riot. He has since granted clemency to several high-profile figures, including Rep. Henry Cuellar of Texas, former Rep. George Santos of New York, Ozy Media CEO Carlos Watson, Silk Road creator Ross Ulbricht, former Illinois Gov. Rod Blagojevich and cryptocurrency executive Changpeng “CZ” Zhao. Most recently, he pardoned five former NFL players convicted of financial and drug-related offenses.

The amendment is being led by Rep. Johnny Olszewski of Maryland, who announced Monday that Rep. Don Bacon of Nebraska has joined as the first Republican co-sponsor. The proposal would create a process allowing 20 House members and five senators to force a vote on overturning a presidential pardon, which would then require a two-thirds majority in both chambers. “This amendment creates a narrow, commonsense check to ensure the pardon power is used fairly and responsibly — regardless of who occupies the White House,” Olszewski said in a statement.

Bacon said the measure would restore balance to the system. “Presidential pardons are an important constitutional authority, but like all powers held by the executive branch, these authorities benefit from the appropriate checks and balances the Constitution envisioned,” he said. He added that concerns over misuse have spanned multiple administrations: “Frankly, it is clear to me the pardon authority has been abused. I’m pleased to cosponsor Rep. Olszewski’s Pardon Integrity Act, a constitutional amendment that establishes a narrow, commonsense guardrail.”

Controversial pardons have been a recurring feature of modern presidencies. For Bill Clinton, it was the pardon of financier Marc Rich. For George W. Bush, it was Scooter Libby. Trump’s first term included pardons for close allies such as Michael Flynn, Roger Stone and Paul Manafort. At the end of his term, President Biden pardoned his son Hunter after his conviction on felony gun charges and guilty plea to tax charges.

Despite renewed attention, the amendment faces steep odds: changing the Constitution requires two-thirds approval in both the House and Senate, or ratification by 38 states, making the proposal a long shot.