Led by West Virginia's attorney general, 21 states have joined a legal effort seeking to overturn Maryland's tough new gun control law.
The Maryland statute has no effect on gun laws in their states, but the attorneys general argue in an amicus brief filed this month that Maryland's law was written too broadly and violates the Second Amendment rights of their citizens.
"States must band together in times when they see citizens' rights being diminished or infringed upon," West Virginia Attorney General Patrick Morrisey said in statement released when he filed the brief. "If the courts decide this law passes muster, it would undermine a core part of the Second Amendment."
Morrisey, who declined to be interviewed, said Maryland's ban on the sale of military-style weapons is akin to "trying to impose a content-based ban on speech. It simply cannot be done."
A federal court ruled that Maryland's ban on 45 types of semiautomatic rifles is constitutional. The coalition of gun owners and gun-rights groups that challenged the law is appealing the decision by the U.S. District Court of Maryland. The attorneys general have joined that effort.
Maryland has not yet filed its response, due by the end of the year.
Legal experts say that while it is generally unusual for states to weigh in on laws that do not directly affect them, it is common in divisive issues such as gun control.
"They don't want certain types of regulations to get court-sanctioned because they're afraid it will become a precedent in their states," said Stephen J. Oren, a Rockville lawyer who chairs the Maryland Bar Association's state litigation section. "So they take the pre-emptive step of filing in cases that don't involve them."
Maryland's gun law, proposed by Gov. Martin O'Malley and passed by the General Assembly in 2013, was among the most stringent enacted after the massacre of 20 children and six adults at an elementary school in Newtown, Conn. It is one of three, all passed after Newtown, that gun-rights activists are fighting in federal courts.
Judge Catherine C. Blake upheld Maryland's ban in August, rejecting the argument that military-style weapons are in common use for self-defense and therefore protected by the Second Amendment. Blake wrote that she considered the ban a legitimate way to improve public safety.
The coalition of gun owners and gun-rights groups asked the 4th Circuit Court of Appeals to review the case. Along with West Virginia, attorneys general from Alabama, Alaska, Arizona, Florida, Idaho, Kansas, Kentucky, Louisiana, Michigan, Missouri, Montana, Nebraska, New Mexico, North Dakota, Oklahoma, South Carolina, South Dakota, Texas, Utah, and Wyoming signed on to the amicus brief.
Like Maryland's, gun laws passed in New York and Connecticut were upheld by federal judges and are now on appeal. Courts have upheld similar bans in California and the District of Columbia.
Maryland Attorney General Douglas F. Gansler's office wrote amicus briefs supporting the laws in New York and Connecticut, but spokesman David Paulson said the state had a clear interest in the outcome there. A court ruling that overturned those bans could have affected Maryland's, he said.
Gansler has also weighed in on laws in other states that might not have directly influenced law in Maryland, including writing briefs to overturn bans on same-sex marriage in other states, Paulson said.
O'Malley spokeswoman Nina Smith said the ban on the sale of assault-type weapons, along with other provisions of the 2013 gun law, was part of a comprehensive plan to reduce gun violence in Maryland.
"A federal judge has already affirmed the constitutionality of this law," Smith said. "This effort by other states won't do anything to reduce violent crime or save lives."
Gun-rights advocates say they worry that lower federal courts appear willing to weaken an individual's right to gun ownership. A landmark 2008 Supreme Court ruling, known as the Heller decision, affirmed that right.
"If the federal courts are trying to open the door after the Supreme Court shut it ... other states, especially attorneys general in pro-gun states, want to weigh in," said Erich Pratt, director of communications for Gun Owners of America.
His group is one of 33 from across the country that, like the 21 attorneys general, have filed legal arguments in support of the appeal.
Pratt contends that Maryland's ban threatens rights beyond that of gun ownership. "If you can have restrictions on the Second Amendment ... then you could have restrictions on other amendments," he said.
Supporters of Maryland's law are expected to add their voices by filing amicus briefs once the state has filed its response to the appeal.
The Brady Center to Prevent Gun Violence is among them. Jonathan E. Lowy, director of the group's legal action project, said other states interfering with Maryland's assault weapons ban strikes him solely as political posturing.
"There's absolutely no interest for West Virginia to have more people in Maryland buying and possessing assault weapons," Lowry said. "There's no court decision that could say the people of West Virginia must have an assault weapons ban. That's not an issue. That's a political decision. There is just no legitimate reason for the attorney general of West Virginia to be fighting the gun lobby's fight."