A flurry of gruesome shootings nearly always brings the issue of gun control back into public debate. That's happening again, in the wake of cop killings in Oakland and Pittsburgh and drug violence in Mexico. A year after the U.S. Supreme Court's decision in District of Columbia v. Heller affirmed the individual right to bear arms, state legislators who want to rein in gun violence are looking for restrictions that will still fly constitutionally.

It's the Mexican situation that seems most likely to result in legislation. Federal officials report that most weapons used by drug cartels in Mexico, where 9,000 people have been killed since the start of 2008, were illegally imported from the U.S., particularly the Southwestern states. The National Rifle Association disputes this, but is not fighting a bill in Texas to increase penalties for gun trafficking. The bill's advocates seem to have sold the argument that this is more a question of border control than gun control. "We don't expect opposition of any significance," says Ryan LaRue, a policy analyst with the Texas Senate's Committee on Administration, which crafted the bill in consultation with Governor Rick Perry.

Passing tougher gun laws in the states where mass shootings have occurred will prove harder. California state Senator Loni Hancock represents Oakland, where four police officers were killed in March in the worst law enforcement tragedy since 9/11. She has introduced a bill to regulate and track ammunition magazines, noting that the technology for doing the tracking has improved in the past decade. The feds tracked movement of ammunition until 1986, but there's essentially no record-keeping now.

But despite efforts such as Hancock's, there's more momentum in legislatures this year to guarantee concealed-weapon carrying rights than to enact new restrictions. Last month, a Gallup poll found that only 29 percent of Americans favor banning handguns--the lowest number in 50 years of polling on that issue.

Of course, the Heller decision made handgun bans a moot issue anyway. So it makes sense for gun-control advocates to focus on things such as registration requirements and trafficking restrictions. Some of the activists are publicly optimistic. "As these incidents continue, particularly these attacks on police, it certainly creates an atmosphere where gun control has much more of a chance than it did a month ago," says Kristen Rand, of the Violence Policy Center. But recent history suggests that outrage over high-profile shooting incidents tends to dissipate in a relatively short time, and there is little evidence so far that the current situation will prove to be much different.