New York Mayor Michael Bloomberg, long an advocate of stricter gun control, is launching a national campaign to repeal “Stand Your Ground” laws, which are on the books in states around the country and make it easier for people to claim self-defense when involved in a violent altercation. Sanford police said George Zimmerman cited the provision in Florida after shooting Trayvon Martin.

Bloomberg, the co-chair of Mayors Against Illegal Guns, held press conferences with key civil rights leaders this week in New York and Washington to announce his push to get these laws reformed or repealed in the more than 20 states that have “Stand Your Ground” provisions. While not written the same way in each state, these laws generally broaden the ability of people to justify using force (both with and without a gun) if they feel threatened.

But the campaign will be very challenging. The National Rifle Association, which supported” the “Stand Your Ground” law in Florida, is one of the most powerful and influential lobbying groups in the country, both in Washington and in state capitals.

And many Democrats, including President Obama, are wary of showing any sign they are against gun rights, worried about losing moderate voters in the Midwest and South. The party has largely dropped the issue of gun control over the last decade and Democrats did not heed Bloomberg’s call for tighter gun laws last year after the shooting of then-Rep. Gabrielle Giffords.

Republicans, both at the national and the state level, are closely-allied with the NRA and opposed to measures that might affect gun rights.

“The NRA’s ‘shoot first’ laws that have passed in 25 states have undermined the integrity of the justice system and done serious harm to public safety,” says Bloomberg.

Since Martin’s shooting, Republicans, including Florida Gov. Rick Scott, have said they will take a closer look at these provisions. Scott has created a task force in Florida.

Many Democrats, including legislators in Florida, are seeking to repeal these laws at the state level. And members of the Congressional Black Caucus want Congress to pass a resolution formally condemning “Stand Your Ground” laws.

But former Florida Gov. Jeb Bush, who signed the provision in 2005, and other strong gun rights supporters say the law is probably not to blame for Martin’s death. They argue Zimmerman may not be able to claim self-defense under the provision if he shot Martin in the manner the teenager’s family has described, with little provocation.

“The ‘stand your ground’ law was a good law when we passed it; it’s a good law now,” former NRA president Marion Hammer told Bloomberg News in a recent interview. “Laws don’t do bad things. People do bad things. Those who attempt to put ‘stand your ground’ on trial do so from a very weak position.”

Her formulation that “people” not “laws” are to blame is familiar; the NRA has longed argued criminals, not guns, result in shootings in America, therefore gun ownership does not need to be restricted. Bloomberg will have to convince Americans otherwise to get the “Stand Your Ground” provisions repealed.

Follow Perry Bacon Jr. on Twitter at @perrybaconjr