The Constitution protects the right of lobbyists to spend money to influence politicians -- a key hurdle prosecutors have to overcome if they want to prove that someone like Jack Abramoff or the circle of elected officials tied to him has committed a crime.
For instance, in cases involving a "quid pro quo" between a lobbyist and a lawmaker, prosecutors must have evidence showing that the transaction crossed the line between federal bribery law -- which bars the offering or acceptance of anything of value in exchange for influence -- and the First Amendment, which specifically protects the right to "petition the Government for a redress of grievances."
Disgraced lobbyist Abramoff pleaded guilty to conspiring to cross that line, drawing prosecutors' attention by breaking enough of the federal rules and laws governing the universe of some 14,000 active lobbyists in Washington.
Regulation of lobbyists falls generally under the Lobbying Disclosure Act (LDA) of 1995 and the Bipartisan Campaign Reform Act of 2002. The LDA states that when its provisions are violated, the secretary of the Senate or the clerk of the House must "notify the United States Attorney for the District of Columbia."
It then becomes the responsibility of the prosecutors to show evidence to a judge or jury that a crime has been committed.
Under the LDA, anyone who makes more than one "lobbying contact" -- an oral or written communication seeking to influence an executive-branch official, member of Congress or congressional staffer -- during a six-month period must register as a lobbyist.
The law requires lobbyists to file twice-annual reports disclosing all money they spent on lobbying. Firms and people who engage in lobbying must include their incomes in the disclosure reports.
Like other U.S. citizens, lobbyists are allowed to contribute directly to political campaigns. The campaign law says anyone can contribute up to $2,000 per election cycle directly to the candidate, up to $5,000 a year to political action committees, up to $10,000 a year to state party committees and up to $25,000 a year to national party committees.
In total, a person can contribute no more $95,000 during a two-year period.
Meanwhile, in addition to the campaign law and the LDA, a separate set of regulations exists to monitor and punish lawmakers before the Justice Department ever gets involved. These regulations are overseen by the House and Senate ethics committees, and chief among them is the rule that any former senator or House member who wishes to become a lobbyist must wait one year from the time that their elected status ends and the time that their lobbying activities commence.
The ethics rules outline the value of "gifts" that lawmakers are allowed to receive from people, lobbyists included, and bar lobbyists from paying for the travel expenses of House members.