By Ian Simpson
WASHINGTON (Reuters) - Gun rights supporters filed a motion on Friday to block Maryland's new gun law, one of the toughest in the United States, from taking effect next week.
The motion, filed in U.S. District Court in Maryland, seeks a court order to block the law, which includes a ban the sale of 45 types of assault weapons.
The plaintiffs, in a lawsuit, claim the law would violate the Second Amendment to the U.S. Constitution, which guarantees the right to keep and bear arms. The suit names as defendants Democratic Governor Martin O'Malley and the Maryland State Police, among other.
A court order "would ensure that defendants do not impermissibly prevent law-abiding citizens from exercising their fundamental right to acquire and possess commonly used firearms in their homes for self-defense," the suit said.
Samantha Kappalman, an O'Malley spokeswoman, said the vast majority of Maryland residents back the law. "The new law will take effect on Tuesday and it will make families safer," she said.
The law, prompted by the December 2012 school massacre in Newtown, Connecticut, requires handgun buyers to undergo safety training and submit fingerprints to obtain a license. The law also limits magazine capacity to 10 rounds, down from the prior 20-round limit.
It bans the sale of 45 types of assault weapons, including all models of the AR-15, the type of rifle used in the Newtown attack, by accused Aurora, Colorado, shooter James Holmes, and by Washington's "Beltway sniper" in 2002.
O'Malley signed the bill into law in May even as opponents, including the National Rifle Association, the powerful gun lobby, vowed to overturn it.
Earlier this month Colorado voters ousted two Democratic state lawmakers over their support for tough gun laws, a major win for gun rights supporters.
(Reporting by Ian Simpson; Editing by Scott Malone and John Wallace)