By Lawrence Hurley

WASHINGTON (Reuters) - The U.S. Supreme Court on Monday left in place gun control laws in New York and Connecticut that ban military-style assault weapons like the one used in last week's massacre at an Orlando nightclub, rejecting a legal challenge by gun rights advocates.

The court's action underlined its reluctance to insert itself into the simmering national debate on gun control. The Supreme Court issued important rulings in gun cases in 2008 and 2010 but has not taken up a major firearms case since.

The justices declined to hear an appeal of an October ruling by the New York-based 2nd U.S. Circuit Court of Appeals that upheld laws prohibiting semiautomatic weapons and large capacity magazines in the two northeastern states.

"Sensible gun safety legislation works. The Supreme Court's action today in declining to hear this appeal affirms that the reforms enacted in Connecticut following the tragedy at Sandy Hook Elementary School were reasonable, sensible and lawful," Connecticut Attorney General George Jepsen, a Democrat, said.

The New York and Connecticut laws, among the strictest in the nation, were enacted after a gunman with a semiautomatic rifle killed 20 young children and six educators in 2012 at Sandy Hook Elementary School in Newtown, Connecticut.

The gunman in the June 12 attack at an Orlando gay nightclub that killed 49 people, the deadliest mass shooting in modern U.S. history, used a semiautomatic rifle that would have been banned under the New York and Connecticut laws.

"The overwhelming majority of responsible gun owners want reasonable and effective gun control legislation," New York Attorney General Eric Schneiderman said. "They know that there is no place for weapons of war on the streets of America. New York's assault weapons ban keeps New Yorkers safer - period."

Schneiderman, a Democrat, urged other states to enact similar laws.

The legal challenge mounted by gun rights groups and individual firearms owners asserted that the New York and Connecticut laws violated the U.S. Constitution's Second Amendment guarantee of the right to bear arms. The court denied the appeal with no comment or recorded vote.

The challengers to the Connecticut law said it banned "some of the most popular firearms in America," guns they said are owned by millions of Americans for the lawful purposes of self-defense, hunting and recreational shooting. The state said these kinds of guns are used in "the most heinous forms of gun violence."

In December, the court declined to hear a challenge to a Illinois town's assault weapons ban. But the justices in March threw out a Massachusetts court ruling that stun guns are not covered by the Second Amendment and sent the case back to the state's top court for further proceedings.

The United States has among the most permissive gun rights in the world. Because the U.S. Congress long has been a graveyard for gun control legislation, some states and localities have enacted their own measures.

In total, seven states and the District of Columbia ban semiautomatic rifles. A national law barring assault weapons expired in 2004. Congressional Republicans and some Democrats, backed by the influential National Rifle Association gun rights lobby, foiled efforts to restore it.

In the aftermath of the Orlando massacre, the Senate was taking up gun legislation on Monday, although the four measures were not expected to win passage.

There is a longstanding legal debate over the scope of Second Amendment rights.

In the 2008 District of Columbia v. Heller case, the Supreme Court held for the first time that the Second Amendment guaranteed an individual's right to bear arms, but the ruling applied only to firearms kept in the home for self-defense. That ruling did not involve a state law, applying only to federal regulations.

Two years later, in the case McDonald v. City of Chicago, the court held that the Heller ruling covered individual gun rights in states.

(Reporting by Lawrence Hurley; Editing by Will Dunham)