2 U.S.C. § 288c — Defending the Senate, committee, subcommittee, member, officer, or employee of Senate

(a) When to defend. Except as subsection (b) says otherwise, once directed under section 288b(a) of this title, the Counsel must: (1) defend the Senate, or a committee, subcommittee, Member, officer, or employee of the Senate, in any civil lawsuit pending in a federal, state, or local court where the Senate (or that committee, subcommittee, Member, officer, or employee) has been sued as a defendant, and where the lawsuit challenges the validity of some official proceeding or action they took — including issuing a subpoena or order — in their official or representative role; or (2) defend the Senate, or such a committee, subcommittee, Member, officer, or employee, in any proceeding over a subpoena or order that was directed at them in that official or representative role. (b) Consent required for individuals. The Counsel may only represent a Member, officer, or employee under subsection (a) if that Member, officer, or employee agrees to it.