Senator Coburn (R-OK) has been dogged in his determination of the "Coconut Road" earmark controversy.  Yet, he's not sure the Senate's vote for an investigation by the Department of Justice will pass constitutional muster.  Coburn spoke to the Anchorage Daily News:

Coburn, who opposes earmarks and has been critical of the Alaska delegation, had asked for a bipartisan House and Senate committee to investigate the earmark. It would then refer its findings to the proper authorities. His proposal had 49 supporters, but needed 60 votes for approval.

Later, Coburn said he feared that the Senate's vote Thursday was unconstitutional. Congress can't order a criminal investigation any more than the Justice Department can investigate violations of congressional rules, Coburn said. It violates the Speech and Debate clause of the Constitution, which keeps investigators from using legislative materials as evidence of wrongdoing in criminal investigations.

"Violating congressional rules is not a crime, yet Congress has just given away its right to police itself with this misguided amendment," Coburn said.

His concerns were echoed by congressional budget and ethics watchdog groups, who say they worry that a criminal investigation won't get at the heart of what is essentially a procedural problem.