Powell v. McCormack(1969) p53
A Congressman was not allowed to be seated because he had some sort of crime on his record….
Whether the power granted to each house in Article I , § 5, to judge the "qualifications of its own Members" includes the power to impose qualifications other than those set forth in the text of the Constitution.
Congress has no power to alter the qualifications in the text of the Constitution.
The Constitution does not allow Congress to impose additional qualification on members of Congress other than those set forth in the text of the Constitution.
The House of Representatives has no authority to exclude any person, duly elected by his constituents, who meets all the requirements for membership expressly prescribed in the Constitution.