Democrats on the Senate Judiciary Committee sent a new letter to Chief Justice John Roberts Jr. Thursday demanding more information on a recent statement about ethics principles signed by the justices.

Thursday's missive is the latest in an ongoing back-and-forth between the committee and Roberts. It started earlier this month when Senate Judiciary Chairman Dick Durbin sent Roberts an "invitation" to testify at a hearing on Supreme Court ethics reform next week. Roberts declined, but attached a "Statement on Ethics Principles and Practices" in his response to the Illinois Democrat.