(Corrects to show Magpul is an ammunition magazine manufacturer, not an ammunition manufacturer)
By Keith Coffman
DENVER, March 21 (Reuters) - Only a day after Colorado's governor signed laws setting limits on ammunition and imposing background checks, gun rights advocates have vowed to sue, some county sheriffs have declined to enforce the measures, and an ammunition magazine manufacturer is leaving the state.
The measures signed into law on Wednesday by Governor John Hickenlooper will ban ammunition magazines with more than 15 rounds, require universal background checks for gun buyers and force gun buyers to pay for their own background checks.
Colorado has seen two of the deadliest mass shootings in U.S. history, and the legislation represented an effort to prevent those types of killings. The measures were also passed during a national debate over firearms violence reignited by the December slayings of 20 children and six adults at a school in Connecticut.
The laws' passages are considered a victory for Democrats in a state where gun ownership is treasured.
The Denver-based libertarian group Independence Institute said it would file a lawsuit either in state or federal court against Colorado seeking to block the measures that are set to go into effect on July 1.
"We're going to court and the people in 2014 are going to have an opportunity to choose a new legislature and a new governor," said David Kopel, research director for the group.
In another challenge to gun-control measures enacted after the Connecticut school shootings, a National Rifle Association affiliate filed a lawsuit on Thursday charging that New York state's laws banning assault weapons and limiting the size of ammunition magazines violated the constitutional right to bear arms.
Ammunition magazine manufacturer Magpul, which has a plant in Erie, Colorado, threatened before the passage of the Colorado bill to leave the state and take away what its executives said were 200 direct jobs and 400 jobs at related companies in its supply chain.
On its Facebook page, Magpul said it would go through with the threat to move, and supporters posted comments inviting them to their own states such as Missouri and Nevada.
"Our transition to a new home will occur in a phased and orderly manner to allow us to continue to serve our customers during the move, as well as to allow an orderly transition for affected employees," the company's statement on Facebook said.
A representative for Magpul did not return calls.
Eric Brown, spokesman for the governor, said in an email that nothing in the bills signed by Hickenlooper would prevent Magpul from "manufacturing here and selling elsewhere."
Meanwhile, a number of county sheriffs in Colorado have said they cannot or will not enforce the new gun control laws, even as the governor's office has directed state officials to give law enforcement agencies technical guidance on how the magazine limits in particular should be interpreted and enforced.
"We expect sheriffs to follow all state laws to the best of their abilities," Brown said.
In July 2012, a gunman opened fire in a crowded theater at the opening night of the Batman movie "The Dark Knight Rises" in the Denver suburb of Aurora, killing 12 people and wounding 58 others.
Colorado was also the site of a 1999 massacre at Columbine High School, where two teenagers shot dead a teacher and 12 other students before committing suicide. (Additional reporting by Joseph Ax in New York; Writing by Alex Dobuzinskis; Editing by Cynthia Johnston and Peter Cooney)