The House Appropriations Committee has just passed an amendment -- the Tiahrt Amendment -- that forbids the sharing of information police need to find the source of guns used in crimes. This amendment is opposed by a broad coalition of police chiefs and mayors, who are desperate to stop the flow of guns into the cities.

Why vote to cripple police efforts? Because the gun lobby, led by the National Rifle Association, demands it. The gun lobby opposes sharing the information on where the guns used in crimes come from because it fears that information would be used to enforce current constraints on gun dealers. What was once a concern for ensuring that hunters would have access to the guns they need for their hobbies has become an obsession that serves criminals and terrorists.

This isn't a complicated story. Guns are not manufactured in cities. For the most part, the guns used in crimes are not even purchased in the cities where the gun crime takes place.

Where do the guns used in crimes come from? They can be traced -- and they have been, by the Bureau of Alcohol, Tobacco and Firearms. According to a BATF report, only a few gun dealers are the source of a bulk of the guns used in crimes. BATF estimates that 1 percent of gun dealers supply 57 percent of the guns used in crimes.

Most gun dealers are law-abiding and responsible. More than eight out of 10 supply no crime guns at all. But a small minority profit from the illegal gun trade. They don't make cursory checks. They ignore the obvious. They peddle large numbers of guns to straw purchasers. Profit is more important than public safety.

BATF's data has been used by police and city officials, such as New York's Mayor Michael Bloomberg, to identify the gun dealers who supply the bulk of guns used in crimes. This freaked out the gun lobby. In rode Rep. Tom Tiahrt (R-Kan.), happy to be of service. He attached a rider to the BATF appropriations bill that prohibited the agency from sharing gun data with police agencies or anyone else unless specifically related to an individual crime. The rider's only purpose was to protect gun dealers operating illegally.

Tiahrt claims he is just trying to protect police and the rights of gun owners. He doesn't mention the rights of those slain by guns -- 32 people every single day. Who gets killed? For the most part, people kill people they know, or they kill themselves. They get angry or depressed, and a gun makes it easy. Add that to violent crime and you get a daily Virginia Tech spread across America.

Bloomberg helped organize mayors and police chiefs to oppose the Tiahrt rider. They simply want BATF to share the data the agency has already collected with local police, so the police can track the source of the guns involved in crimes. If these guns come from widely disparate places, nothing much can be done. But if one or two unethical dealers are the source, surely the entire society -- including the NRA's members, if not its rabid officers -- has a stake in cracking down on those dealers.

George Bush keeps saying that Sept. 11 changed everything. But it did not change the NRA's offensive against commonsense regulation of the sale of guns in this society. And it didn't change the pandering to that lobby by the president and Congress. The politicians have made it safe for terrorists to buy assault weapons -- no longer banned -- from shady dealers who don't make the checks needed for public safety. For this crowd, Sept. 11 means cracking down on the cosmetics grandmothers take on airplanes, not on gun dealers peddling the guns used in crime.

This isn't a partisan issue. Both Democrats and Republicans are terrorized by the gun lobby.

Standing up to this lobby is a matter of common sense and courage -- both of which seem to be in short supply in Washington.

© 2007 The Chicago Sun-Times