House Democrats subpoenaed former White House Counsel Harriet Miers and White House chief of staff Joshua Bolten to get their perspective on the U.S. Attorney purge scandal. They refused. House Democrats sought support from the Justice Department in enforcing congressional subpoenas. It refused.

Today, left with limited options, the House Judiciary Committee filed a civil suit to compel Miers’ and Bolten’s testimony. It sets up an extremely interesting legal showdown.

The lawsuit filed in federal court says Miers is not immune from the obligation to testify and that she and Bolten must identify all documents that are being withheld from Congress.

In a statement announcing the lawsuit, House Judiciary Committee Chairman John Conyers said, “We will not allow the administration to steamroll Congress.”

Conyers said he is confident the federal courts will agree that the Bush administration’s claims to be immune from congressional oversight are at odds with constitutional principles.

Judiciary Committee Chairman John Conyers (D-Mich) noted, “It is extremely rare that Congress must litigate in order to enforce subpoenas and no compromise can be reached. Unfortunately, this Administration simply will not negotiate towards a compromise resolution so we must proceed.”

White House Press Secretary Dana Perino responded, “The confidentiality that the president receives from his senior advisers and the constitutional principle of separation of powers must be protected from overreaching and we are confident that the courts will agree with us.”

It probably won’t surprise you to hear that Conyers’ argument is more compelling.