It's unclear.

"Presidents do have broad — but not unlimited — pardoning power."

"The framers of the Constitution put the presidential pardoning power into the founding document in order to correct unjust prosecutions or convictions — both of which had occurred frequently in England.

At the Constitutional Convention, there was a proposal to exempt treason from the president's pardoning power — the notion being that if a president conspired with subordinates to commit treason, he should not be able to protect himself by pardoning fellow conspirators." [1]

[1] https://www.npr.org/2017/07/29/539856280/could-trump-pardon-...