The bill, known as the Castle Doctrine, made it harder to prosecute or sue people who used deadly force against intruders inside their houses. But the Wisconsin legislators, urged on by the National Rifle Association in a series of meetings, wanted it to go further. They shaped an amendment that extended the bill’s protections to include lawns, sidewalks and swimming pools outside the residences, as well as vehicles and places of business.
That expanded bill, passed with little debate by the Legislature and signed in December by Gov. Scott Walker, a Republican, is the newest of more than two dozen so-called Stand Your Ground statutes that have been enacted around the country in recent years. Those laws are now coming under increased scrutiny after Mr. Martin was shot to death by George Zimmerman, a neighborhood watch coordinator, in late February. Similar legislation is pending in several other states, including Alaska, Massachusetts and New York.
Though the laws vary in their specifics and scope, they expand beyond the home the places where a person does not have a duty to retreat when threatened, and they increase protection from criminal prosecution and civil liability. All contain elements of the 2005 Florida statute that made it difficult to immediately arrest Mr. Zimmerman, who has said he shot Mr. Martin, who was unarmed, in self-defense.
Critics see the laws as part of a national campaign by the National Rifle Association, which began gathering on Thursday in St. Louis for its annual meeting, to push back against limits on gun ownership and use. That effort, they say, has been assisted by conservative legislators in states like Wisconsin, and by the American Legislative Exchange Council, which has promoted model legislation based on Florida’s law; the council, known as ALEC, is a conservative networking organization made up of legislators, corporations like Walmart, a large retailer of long guns, and interest groups like the rifle association.
The success of the campaign is reflected in the rapid spread of expanded self-defense laws as well as laws that legalize the carrying of concealed weapons. Only one state, Illinois, and the District of Columbia now ban that practice, compared with 19 states in 1981. Bills pending in several states that would allow concealed weapons to be carried on college campuses, in churches, in bars or at other sites would further weaken restrictions, as would either of two federal bills, now in the Senate, that would require that a permit for carrying a concealed weapon that was granted by any state be honored in all other states.
“Both directly and with cutouts like ALEC, the N.R.A. is slowly and surely and methodically working at the state level to expand the number and kind and category of places where people can carry concealed, loaded weapons and use them with deadly force,” said Mark Glaze, director of Mayors Against Illegal Guns, a bipartisan coalition of more than 650 mayors that has not taken a position on the Stand Your Ground laws.
Repeated requests to speak with N.R.A. officials about Wisconsin’s law or Stand Your Ground laws more generally met with no response.
In Wisconsin, as in other states, the passage of an expanded self-defense law was helped by the 2010 elections, which vaulted conservative Republicans into office. In Pennsylvania, for example, a Stand Your Ground law passed the Legislature in 2010 but was vetoed by Gov. Ed Rendell, a Democrat. Introduced again last year, the bill was signed by his Republican successor, Tom Corbett.
In Wisconsin, a narrower version of the legislation had languished and died in previous sessions. But with a Republican governor and Republicans dominating both houses of the Legislature, several state lawmakers said that the success of the bill and the expansion amendment promoted by the N.R.A. seemed assured.
“I think it’s only normal they assumed this could be their year,” said Representative Dean Kaufert, a Republican who introduced the legislation, speaking of the rifle association.
Darren LaSorte, a lobbyist for the rifle association, wanted the legislation, like Florida’s law, to extend protection to any place where a person had a legal right to be, said several Republican lawmakers who met with Mr. LaSorte. But having been successful in getting an earlier bill passed to allow the carrying of concealed weapons, Mr. LaSorte accepted a compromise.
“It was almost a ‘we’ll take what we can get’ kind of mode,” Mr. Kaufert said. In its final form, the law contained language that closely tracked some parts of the Florida bill.