Every state but Illinois lets residents carry a concealed weapon. But some states impose much stricter rules than others. This important prerogative is now in danger, thanks to U.S. House legislation to make all concealed-carry licenses valid in all states permitting them. This bad idea was killed once, just two years ago, when it was introduced by Sen. John Thune (R.-S.D.). Now, Representatives Cliff Stearns (R.-Fla.) and Heath Shuler (D.-N.C.) are reviving it as the National Right-to-Carry Reciprocity Act.

The act would force states to welcome gun-toting visitors who, as residents, might be barred from carrying the same guns. New York and California, for example, would have to tolerate armed people licensed by Utah. Yet Utah does not require permit holders to pass a live-fire test on a shooting range. So Nevada recently decided to drop Utah from the list of states whose permits it will honor. Essentially, Nevada recognizes only permit holders who meet its own higher standards. (Some 30 states do recognize Utah’s permits; kudos to common-sense Nevada.)

A national reciprocity law would loosen standards across America, and probably expand the ranks of permit holders. Utah, for instance, has granted licenses to thousands of non-residents, including foreign citizens, says the Brady Campaign to Prevent Gun Violence. The ease of moving across state lines could bring a flurry of new applicants.

The dangers to citizens, including police officers, would accordingly rise. In traffic stops, the police are apt to encounter more gun-wielding people. Yet the House bill contains no mechanism to help them verify out-of-state permits. Potential criminals and gun traffickers could easily be waved on their way.

The Brady campaign points to studies showing that concealed-carry laws do not reduce crime, and may well do the opposite. In the past four years, it notes, permit holders have shot and killed more than 300 people, including nearly a dozen police officers. Many have been arrested for crimes after obtaining permits.

Currently, most states set minimum age requirements for permit holders, and require gun-safety training. Most also bar people convicted of violent crimes, such as sexual assaults, from carrying concealed weapons. These are valid standards aimed at protecting the public. Congress, rather than bowing to yet another demand of the National Rifle Association, should honor states’ concerns.