(Bloomberg) -- Former Vice President Mike Pence is pledging to take his challenge to a grand jury subpoena from the special counsel investigating Donald Trump and his allies to the US Supreme Court if needed, declaring he’s protecting the separation of powers under the US Constitution.

Special Counsel Jack Smith subpoenaed Pence as part of his investigation into efforts by Trump and others to overturn the 2020 election. Pence said just as it was wrong for Trump to pressure him to reject Electoral College votes from key swing states when he presided over a joint session of Congress on Jan. 6, 2021, it’s wrong for the executive branch to compel him to respond when he was acting as a legislative official.

“That runs against literally hundreds of years of not only American law, but common law,” Pence told reporters after an event in Minnesota on Wednesday, according to a video posted online. “We’ve got to stand for that principle because it’s a separation of powers. And that’s why we’re prepared to take this fight into the court and, if needs be, take it to the Supreme Court of the United States.”

There’s a robust history of members of Congress successfully invoking that constitutional shield against criminal inquiry and civil lawsuits, but whether a former vice president can claim it is a largely untested question. 

Article I of the Constitution states that “the Vice President of the United States shall be president of the Senate,” but in modern times those duties have usually involved breaking a tie in the chamber and presiding over the receiving and counting of Electoral College votes, which was what Pence was doing when Trump’s supporters attacked the US Capitol on Jan. 6. 

Pence, who is considering a campaign for president in 2024, told reporters that it’s his understanding Trump would seek to challenge the subpoena on grounds of executive privilege, but “that’s not my fight. My fight is on the separation of powers.”

“I’m going to fight the Biden DOJ subpoena to appear before the grand jury because I think it’s unprecedented and it’s unconstitutional,” Pence told reporters.

The former vice president also declined to testify before the House committee investigating the Jan. 6 attack based on the separation of powers. He told CBS in an interview in November that Congress “has no right to my testimony.”

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