OVERVIEW: The July 20 shooting at a suburban Denver movie theater that killed 12 people has prompted Democratic leaders in at least three large states to push for tighter restrictions on assault weapons and the purchase of large amounts of ammunition. While California, New York and Illinois push proposals, gun control hasn't gained traction in Congress and on the presidential campaign trail.

PROPOSED GUN RESTRICTIONS: California lawmakers introduced bills that would make it more time-consuming to reload assault weapons with ammunition magazines and require dealers to report purchases of large quantities of ammunition to law enforcement authorities. Two New York lawmakers are proposing wide-ranging restrictions that limit firearms purchases to one a month, mandate a firearms safety course for gun buyers and prohibiting the sale or purchase of more than 500 rounds of ammunition during a 30-day period. Illinois Gov. Pat Quinn wants a strict ban on assault weapons.

WHAT THEY SAY: "If there's no action in Congress, we better do something here and hope it catches fire in other states." — Leland Yee, Democratic state senator in California.

FEDERAL LAW: The 1994 ban on assault weapons expired in 2004, during George W. Bush's presidency. It has not been revived.

CONGRESS: A U.S. senator and representative, both Democrats, introduced a bill in Congress after the Aurora, Colo., shooting that would prohibit the general public from buying thousands of rounds of ammunition by mail or online, but it has virtually no chance of success. The Republicans who control the House of Representatives have not indicated a desire for more gun laws. Senate Majority Leader Harry Reid, a Democrat, said there are no plans for a debate over gun control in that chamber.

PRESIDENTIAL CAMPAIGN: President Barack Obama and Republican presidential candidate Mitt Romney are not advocating for additional gun laws. Instead, they have said existing laws should be more rigorously enforced.

WILL THE PROPOSALS GO ANYWHERE? Because most state legislatures have finished their annual sessions, the gun proposals this summer are most likely to be taken up in earnest when lawmakers return to business in 2013. Democrats control both legislative houses and the governor's office in California and Illinois, increasing the prospects for success. Republicans control the New York Senate and have opposed measures by the Democratic-controlled Assembly. But Democratic Gov. Andrew Cuomo says gun control will be "at the top of my list" next year and says the Senate's Republican majority may be ready to support some gun control measures.