The Senate ethics committee took 10 months to decide that it would not take action against Vitter because he was not in the Senate when his calls to Palfrey's service took place and that he did not, in soliciting a prostitute, abuse his office as a senator.
The House Committee on Standards of Official Conduct did not investigate Vitter, presumably because he was no longer a member of the House.
But Rep. John Murtha, D-Pa., is still in the House. He has come under fire for steering defense contracts to friends and former staffers. There is also no House ethics investigation of Murtha, who chairs a powerful appropriations subcommittee and whose former staffers are under federal investigation in connection with the lobbying scandal. Government groups from the right and left have called for an inquiry into Murtha.
But the House ethics committee does not accept outside requests for investigation. House members tried to make their ethics process more accountable in 2008 when they created a special committee of non-lawmakers as a sort of grand jury for House ethics issues. Sloan argues that since the committee lacks subpoena power, it is ineffective.
The Senate ethics committee pledges to launch a preliminary inquiry whenever an ethics complaint is lodged. The results of those inquiries are rarely made public and the committee does not publicize complaints.
Sloan would like to see an entirely independent body set up to investigate congressional misconduct.
The Constitution gives the House and Senate the responsibility to police their members.
"Each House may determine the rules of its proceedings, punish its members for disorderly behavior, and, with the concurrence of two thirds, expel a member," reads Article I of the Constitution.
Both the Senate ethics committee and the House Committee on Standards of Official Conduct are made up of equal numbers of Republicans and Democrats, a bipartisan gesture in a place where the majority usually rules.
Only five House members have ever been expelled, including, most recently, Democratic Rep. James Traficant of Ohio in 2002. He was recently released from five years in prison for corruption.
No senator has been expelled since the Civil War, although several have come close. Most lawmakers in that much trouble resign before they are expelled.
And all this is not cause for alarm, according to Stan Brand, a former House counsel and expert on congressional ethics.
"It is supposed to be a quasi-judicial process and parts of it look like a judicial process," said Brand. "On the other hand, it takes place in a political body and it's subject to the drafts of political influence."
And if the system were not so opaque, ethics investigations could be used as political weapons.
There is a tendency on the part of both committees to give deference to federal and state judicial systems investigating lawmakers, a practice decried by Sloan.
"Not everything that violates House or Senate rules is also a crime," she said. "Our standard for House and Senate members shouldn't be that they avoid indictment."
Indeed, indictment can cause the ethics committees to stand down. Rep. William Jefferson was recently convicted of taking bribes. He was voted out of office in 2008, but the House ethics committee had suspended its investigation of him long before.