Hear that sound? It’s the squealing and squeaking of DC lobbyists seeing their influence curtailed:

H. Stewart Van Scoyoc, founder of one of the biggest lobbying firms in Washington, spent an anxious morning with his lawyer last week assessing the far-reaching ethics and lobbying rules Congress had passed the day before.

The first worry was what lobbyists are calling the new “temptation rules.” Not only do they bar lawmakers and aides from accepting any gifts, meals or trips from lobbyists, they also impose penalties up to $200,000 and five years in prison on any lobbyist who provides such freebies.

And worse still for Mr. Van Scoyoc, under the new law he is required to certify each quarter that none of the 50 lobbyists in his firm bought so much as a burger or cigar for someone on a lawmaker’s staff…

The new law has quickly sent a ripple of fear through K Street. It comes amid signs that federal prosecutors are taking a newly aggressive approach to corruption cases — including treating campaign contributions as potential bribes.

But it gets even better:

By requiring them to certify the good behavior of their employees, the law puts lobbyists at new legal risk and could subject them to new pressure from prosecutors. And new centralized disclosures of lobbyists’ campaign contributions, fund-raising activities and even their achievements — in the form of Congressional earmarks in spending bills — make it only easier for federal investigators to paint unflattering portraits of lobbyists’ influence.

And better still:

One lobbyist, who would speak only anonymously to avoid attracting the attention of prosecutors or rivals, said he had started sending himself date-stamped e-mail to create a record of every phone conversation he had with a lawmaker. Then he stopped making campaign contributions.

Another lobbyist recently scaled back the menu at a breakfast briefing for lawmakers, offering bagels and cream cheese instead of ham and eggs. The rules permit lobbyists to provide refreshment of “only nominal value.” The House ethics committee guidelines suggest “light appetizers and drinks, or soda and cookies,” a standard that is known as “the toothpick test.”

The firm also advised a client distributing flashlights on Capitol Hill — to promote government openness — to make sure not only that they cost less than $10 each but also that they looked cheap, to avoid the appearance of impropriety.

And the “staff briefing” — in which a lobbyist enticed Congressional staff members to hear a talk about some dry legislative concern by offering pizza — has become extinct. No one will come without the free food.

This is a good start on the supply end of the money chain that corrupts our politics. Now it’s time to work on the demand end — by making money less necessary to win elections.