The House agreed Wednesday to ask the Justice Department to investigate the now infamous Coconut Road earmark, but don’t hold your breath waiting for indictments.

The Constitution’s Speech or Debate Clause, a recent court ruling and aggressive efforts by the House general counsel make it exceedingly difficult for federal prosecutors to investigate — let alone prosecute — members of Congress or their staffs for wrongdoing that may have occurred in the legislative process.

The House voted 358-51 Wednesday to ask the Justice Department to look into how staffers for Rep. Don Young (R-Alaska) managed to get an earmark for a Florida highway interchange inserted into a 2005 transportation bill after it passed both chambers of Congress.

Even Young himself voted in favor of the request. “I welcome, if you want to ‘welcome,’ an investigation into this House,” Young said.

But critics contend that House members may be so open to an investigation precisely because they know it won’t go anywhere. “It’s laughable,” said Melanie Sloan, the executive director of Citizens for Responsibility and Ethics in Washington. “They want the headlines, so they’re going to do this. But it’s an absolute farce.”

Stanley Brand, a former general counsel for the House, said the barriers to investigation and prosecution — especially in the Coconut Road case — arise straight from the Constitution. “The Speech or Debate Clause would prevent Justice from questioning lawmakers about what happened on the House floor or outside in the enrollment process,” he told Politico this week. “That’s the essential nature of the crime, or the alleged crime.”

“There’s nothing outside the scope of the clause,” Brand added. “I don’t know what they’re doing.”

In addition to the Speech or Debate Clause itself, Sloan said that a federal appeals court ruling that limits prosecutors’ access to materials collected in a raid of Louisiana Democratic Rep. William Jefferson’s Rayburn office has made it nearly impossible to investigate any member who has abused the office in his official capacity.

In seeking — unsuccessfully — to have the Supreme Court reverse that ruling, the Justice Department argued that federal prosecutors would have difficulty conducting future public corruption investigations that would otherwise “serve a vital role in protecting the integrity of our democratic government.” Sloan suggested this week that the ruling has hampered investigations of Republican Reps. John Doolittle of California, Jerry Lewis of California and Rick Renzi of Arizona.

“Bob Ney would never go to jail today,” Sloan said, referring to the former Ohio Republican who pleaded guilty in 2006 to accepting gifts from jailed former GOP lobbyist Jack Abramoff in exchange for legislative favors.

Sloan also complains that the House general counsel has taken a much harder line defending members and aides from these inquiries since the Jefferson raid. Earlier this year, she wrote to House General Counsel Irvin B. Nathan complaining about his defense of a Lewis staffer who had been subpoenaed, as well as his objections to a request by law enforcement officials in Florida to access computers used by former Rep. Mark Foley (R-Fla.).

In a letter to House Speaker Nancy Pelosi (D-Calif.) and Minority Leader John A. Boehner (R-Ohio), Sloan accused the congressional leadership of “abetting illegal conduct.” Sloan draws parallels between the legal positions taken by the House attorneys and the sweeping “executive privilege” claims asserted by the Bush White House.

In response, Nathan and Deputy General Counsel Kerry W. Kircher said they were only protecting members and aides under the guidelines laid out in the Constitution. “The positions taken by this office are not designed [for], and have not had the effect of, shielding any member from the criminal justice system,” they said.

Last year, the House fought 13 subpoenas issued to members of both parties in the criminal case against California businessman Brent Wilkes, the defense contractor who was ultimately convicted of offering bribes to jailed ex-Rep. Randy “Duke” Cunningham (R-Calif.).

Making matters worse for those who want to see members investigated, the House ethics committee remains largely paralyzed this year, leaving it almost impossible for lawmakers to police themselves.

Pelosi initially recommended that the Committee on Standards of Official Conduct review the Young earmark but reversed course days later and backed the idea of a Justice Department probe.

Similarly, Republican leaders who opposed the Senate action let Wednesday’s vote occur without a fight, even though it targets one of their own and despite the fact that many privately seethe at the jurisdictional privilege lawmakers are surrendering by making this recommendation.

The Senate voted in April to direct the Justice Department to investigate whether Young or his staff abused the legislative process to alter the language of a nearly $300 billion transportation bill after members approved the measure so that an earmark that was supposed to be aimed at highway improvements was redirected to fund a study of an interchange. The New York Times linked that legislative action to a local developer whose properties would have benefited from the interchange. The developer, Daniel J. Aronoff, helped raise $40,000 for Young’s reelection efforts that same year.

Young, who served as chairman of the House committee with jurisdiction over that road bill, defended his actions in a lengthy floor speech Wednesday. Young said he had no influence over late changes made to the transportation bill and suggested — before voting to approve the Senate measure — that it amounted to “meddling” by the other chamber.

“I have been the subject of much innuendo concerning my intent and motivation with this project,” he said. “These accusations have little, if any, connection with what actually occurred.”