Guns laws were the latest focus of the US presidential campaign, with Republican front-runner Mitt Romney telling the largest US gun rights lobbying group that President Barack Obama is not protecting gun owners. Without offering details, Romney said Obama would likely act to erode gun owners' rights — a sensitive thought for the millions of Americans who are passionate about the constitutional right to bear arms. They overlap with the conservative core of the Republican party that remains skeptical about Romney, and with his closest challenger stepping out of the race days ago, the former Massachusetts governor wants to win their solid support before the November election. “We need a president who will enforce current laws, not create new ones that only serve to burden lawful gun owners,” Romney on Friday told thousands of National Rifle Association members for their annual convention. “President Obama has not. I will.” Obama has said relatively little about firearms, deeply disappointing gun-control groups. Appearing before the NRA is obligatory for Republican candidates because the group has massive resources to use in support of gun laws — and candidates — that it favors. Romney is the presumptive Republican nominee after Rick Santorum left the race days ago, but his relationship with gun owner groups is uneasy. Running for the Senate in 1994, Romney said: “I don't line up with the NRA.” A decade later he became a lifetime NRA member. Another Republican candidate, Newt Gingrich, the former speaker of the US House, addressed the NRA convention after Romney, saying the United Nations should adopt a treaty “to extend the right to bear arms to every person on the planet.” Such “human rights,” Gingrich said, would reduce rapes and child killings worldwide. The right to bear arms is guaranteed by the US Constitution, although the country is fiercely divided over how exactly to interpret the Second Amendment that protects gun possession. The uproar over the recent shooting of 17-year-old Trayvon Martin at the hands of a neighborhood watch volunteer in Florida has galvanized pro- and anti-gun control activists alike. Another case drawing headlines involves two men charged with murder and hate crimes for a shooting spree in Oklahoma, in which three blacks were killed and two wounded. Romney's campaign said Obama has appointed judges, including Supreme Court Justices Elena Kagan and Sonia Sotomayor, who have supported moves such as placing temporary limits on importing semiautomatic assault weapons. The campaign said Attorney General Eric Holder has not adequately backed people's rights to own and use firearms.