Sen. Kit Bond (R-Mo.) has resigned in protest from a bipartisan panel looking into Bush-era interrogation techniques.

The Missouri Republican is part of a bipartisan investigation headed by Senate Intelligence Committee Chairwoman Dianne Feinstein (D-Calif.), the Washington Times reports. The goal of the panel is to explore and explain interrogation policies but not to punish possible violations.

Bond says Attorney General Eric Holder's decision to appoint a special prosector undercuts the panel's work, since potential witnesses might fear that speaking out could lead to criminal prosecution.

"DOJ sent a loud and clear message that previous decisions to decline prosecution mean nothing and old criminal charges can be brought anytime against anyone," Bond said. "Against these odds, what current or former CIA employee would be willing to gamble his freedom by answering the committee's questions?"