WASHINGTON -- California forbids the sale of assault weapons. Florida mandates a three-day wait before handgun purchases. And while Texas and Kansas don’t require dealers to apply for licenses, Missouri and Idaho don’t regulate much of anything at all when it comes to firearms.

In America, thousands of laws, rules and regulations at the federal, state and local levels dictate who can buy, sell, possess and transport firearms; everything from hunting rifles to the type of high-tech guns found on battlefields.

Policies vary by states, even within states, with some lawmakers choosing to ease requirements as a reflection of long-held traditions about the role guns have in society.

The patchwork of laws across the nation is prompting gun control activists to push lawmakers in Washington to create a uniform, nationwide system for firearms.

“States can’t do it alone,” said Mark Glaze, director of Mayors Against Illegal Guns, a coalition of 800 leaders founded by New York Mayor Michael Bloomberg.

President Barack Obama is calling for a divided Congress to pass the nation’s most aggressive gun control plan in generations, following the December rampage in Newtown, Conn., that claimed 26 lives, including 20 children. Police believe shooter Adam Lanza stole the guns he used at an elementary school from his mother.

The Senate has launched hearings, but some lawmakers – Republicans and Democrats from gun-friendly states – are concerned that additional restrictions might stand in the way of the Second Amendment right to keep and bear arms.

“I’m not going to fight hysteria with hysteria,” said Kieran Donahue, sheriff in Canyon County, Idaho, who said he will not enforce new regulations if they pass. “Each and every day, law enforcement officers in our communities put their lives on the line to prevent gun violence and uphold the Constitution. Those men and women don’t have time for hollow political posturing.”

Dan Gross, president of the Brady Center to Prevent Gun Violence, said state laws do have an impact, but that criminals are like water and can find their way around state borders. For example, most guns used in crimes in California, which has some of the most restrictive gun laws in the nation, flow from nearby Nevada and Arizona, which have few regulations.

That means states and cities with strict gun control laws may still have more crime and violence than other jurisdictions with little regulation.

“Anything that eases the ability to get a gun is important to do on a federal level,” Gross said.

Many states do not keep track of the number of guns residents legally own, so it’s impossible to know how many there are. Some states keep a record of background checks performed for purchases, but not all purchases require a check.

States differ on virtually every law they can write on guns: How many handguns can someone buy? Do you need a permit for purchase? Can a person own a large-capacity magazine? Who can carry a concealed weapon? Is a buyer required to know firearm safety? Can someone carry a gun in a school, prison, courthouse, bar, church, hospital, polling place, stadium, the state capitol?

And to complicate matters further, different states use different definitions for everything, from assault weapons to a large-capacity ammunition magazine.