TRENTON - New Jersey will become the fourth state in the nation to limit handgun purchases to one every month. Gov. Corzine signed the controversial measure into law yesterday.

Trenton Mayor Doug Palmer joined Corzine and called on Pennsylvania to become No. 5. The law, which is aimed at slowing gun trafficking, would make life safer in New Jersey and neighboring states by fighting trafficking, he said.

"I just hope Pennsylvanians would make it safer for us by passing this bill," Palmer said at a ceremony outside Trenton City Hall.

The law aims to impede "straw purchasers" - people who have clean records and buy guns legally, then pass them to criminals. The law will take effect in early January but could see some changes before then. A task force is reviewing its potential impact and will make recommendations this fall.

Corzine and gun-control advocates argue that roughly a quarter of what they call "crime guns" recovered in New Jersey come from within the state. It's not clear how many of those came from the type of multiple purchases that Corzine wants to stop. When pressed, the governor said there is anecdotal evidence that people with clean records are making large purchases to help criminals.

"Nothing is more dangerous than to have the proliferation, the vast proliferation, of guns in the hands of individuals who want to perpetrate violence in our communities," Corzine said.

The law would limit handgun purchases to one every 30 days, to a maximum of 13 a year, because of timing quirks. Rifles and other long guns would not be affected.

Exceptions have been carved out for collectors, and a task force has begun meeting to determine if amendments are needed to ensure that people who may need more than one handgun each month - such as competitive shooters - are not restricted.

Critics say the law would impinge on the constitutional rights of law-abiding citizens in New Jersey, which already has some of the most strict gun laws in the nation.

"Trying to reduce gun crime by rationing guns to law-abiding citizens is as absurd as trying to reduce drunk driving by rationing cars to non-drinkers," Scott Bach, president of the Association of New Jersey Rifle and Pistol Clubs, wrote in an e-mail.

Efforts to enact a similar law in Pennsylvania have failed, and Philadelphia saw its one-handgun-a-month ordinance struck down in court.

Gov. Rendell "couldn't agree more with Gov. Corzine, and he's glad New Jersey was able to sign that important legislation into law," spokesman Ken Snyder said yesterday. Prospects in Pennsylvania for the same legislation to pass are "more difficult," he said.

The nine-person review panel includes two Gloucester County Democrats: Assemblyman John Burzichelli, who voted against the bill, and Sen. Fred Madden, who supported it only after receiving assurances that the task force would study its impact. Burlington County prosecutor Robert Bernardi is also on the study team.

California, Maryland, and Virginia have similar laws.