A legal shield written by Congress to benefit the firearms industry is posing unexpected hurdles for parents in Newtown, Connecticut, and victims of other mass shootings who want to use the courts to hold gun makers accountable and push them to adopt stricter safety standards.

The law, approved in 2005 after intense lobbying by the National Rifle Association, grants gun companies rare protection from the kind of liability suits that have targeted many other consumer product manufacturers.

It was introduced amid a wave of lawsuits brought by city governments arguing that gun companies had created a “public nuisance” by encouraging the proliferation of weapons. Advocates for gun makers said such suits threatened to destroy the industry and imperil Americans’ constitutional right to bear arms.

But over the last eight years, the legal shield has increasingly been used to block a different type of legal action — suits brought by victims and their families alleging that gun makers had failed to equip their firearms with proper safeguards.

Lawyers for victims of mass shootings, such as the massacres Dec. 14 at Sandy Hook Elementary School in Newtown, and last summer’s shooting in an Aurora, Colorado, movie theater, say they have been surprised by the legal constraints they would face in challenging the gun industry.

“It makes no logical sense,” said Veronique Pozner, whose 6-year-old son, Noah, was one of the 20 first-graders killed at Sandy Hook. “If their wallets were threatened, they would have a greater interest in making firearms safer.”

Pozner, who has been eyeing a lawsuit, has been discussing the gun industry’s special protections with a lawyer she and other Newtown parents recently retained. “I am looking at anything that can be done to prevent this from happening to another family,” she said in an interview this week, describing the searing memories of her fallen son. “I don’t want his life to be a statistical blip.” Pozner said she wants to press the maker of the semi-automatic rifle used in the crime for failing to install a high-tech safety device that might have prevented Adam Lanza from firing the gun he took from his mother.

Marc Bern, a New York trial lawyer representing family members of Aurora victims, said the gun law severely limits his clients’ options. He is pursuing a case against the movie theater company, though some of his clients had expressed interest in trying to pursue companies that provided guns or ammunition to the shooter.

“We looked at the gun industry, but they were able to insulate themselves with this law,” Bern said. “It is absolutely outrageous that the gun industry is not accountable when virtually every other industry in this country is accountable.”

Officials from the NRA and the gun industry defend the law as a necessary step to protect U.S. companies from costly and unfair litigation that seeks to blame manufacturers and sellers for crimes they did not commit.

Lawyers representing victims in Newtown and other recent shootings, however, say they do not necessarily seek to hold gun makers liable because a gun was used to commit a crime.

These lawyers say they are seeking safety improvements like those that resulted from decades of suits against the auto industry that argued carmakers could be liable for damages if they failed to adopt feasible safety measures. And just as legal action helped lead automakers to add seat belts and airbags, potential litigants in gun cases say they want firearms makers to add readily available safety features, like biometric locks that allow a gun to be fired only by its licensed owner.

Yet when plaintiffs have brought a range of lawsuits against gun companies, they have run up against the industry’s unusual liability shield.

In 2009, for instance, the Illinois Supreme Court rejected claims by the family of a child killed by his 13-year-old friend, who was playing with his father’s loaded Beretta 9mm pistol. The family argued that the gun’s design was flawed because the device meant to register ammunition in the chamber was inadequate and the company should be held responsible. But the court ruled that the company was protected by the industry’s legal shield.

Now, the massacre at Sandy Hook Elementary School is focusing new attention on the gun liability law, called the Protection of Lawful Commerce in Arms Act. Some Democrats in Congress are pushing legislation, sponsored by California Democratic Rep. Adam Schiff, to roll back the law.

Lawrence Keane, general counsel of the Newtown-based National Shooting Sports Foundation, the industry’s trade organization, noted that Congress adopted the law with “overwhelming” majorities and predicted that any repeal effort will fizzle.

The law prohibits suits against gun dealers and manufacturers “for the harm caused by those who criminally or unlawfully misuse firearm products.” It applies not only to federal courts, but actions at the state and local level as well.

While far-reaching, the law allows liability suits to proceed in rare cases where a manufacturer or seller knowingly broke federal laws governing the sale and marketing of guns and in cases involving an alleged defect in the design or manufacture of the weapon, such as a malfunctioning trigger.

Advocates for gun companies say the law is working properly if it is thwarting suits that seek to find fault with law-abiding gun sellers or makers.

“Since its enactment, we have seen state and federal courts across the country dismiss personal injury and wrongful death lawsuits arising out of criminal or unlawful firearm use because it is simply unfair to hold manufacturers and distributors responsible for the wrongful acts of others,” said Craig Livingston, a lawyer who has represented gun manufacturers in the Illinois case. “While legitimate product liability suits are being allowed to proceed, those in which an injury or death was caused by the intentional discharge of a firearm are not. That is exactly how Congress drew it up.”

The NRA played a major role in securing passage of the law, besting other influential groups like the American Bar Association, which had argued that the measure would infringe on the traditional right of Americans to seek redress in the courts.

At the time of its passage, NRA Executive Vice President Wayne LaPierre called the measure “the most significant piece of progun legislation in 20 years,” adding that “history will show that this law helped save the American firearms industry from collapse under the burden of these ruinous and politically motivated lawsuits.”

The vote in Congress came after years of effort by the NRA and its allies. The liability exemption sets firearms apart from nearly every other industry. A handful of products have been granted limited immunity. Vaccine makers, for instance, have certain protections against suits from injured patients, as do Internet service providers shielded from many suits over defamation or copyright infringement.

Legal scholars say the breadth of the protections granted to the gun industry is rare for consumer product manufacturers.

“To give a product manufacturing industry a substantial immunity is really distinctive,” said Robert Rabin, a Stanford University law professor who specializes in product liability cases. “The auto industry, the home supply industry, none of the industries that manufacture products that are ubiquitous in the market have that sort of insulation from liability.”