Just days before the anniversary of the Sandy Hook Elementary School shooting, the Senate extended a ban on undetectable firearms but declined to tighten any of the law's restrictions.

The legislation -- which continues a 10-year prohibition on the manufacture, sale or possession of guns that cannot be detected by X-ray machines or metal detectors -- was passed by "unanimous consent," or without a roll call vote. President Barack Obama signed it into law Monday night.

Gun rights advocates had opposed making any modifications to the law, known as the Undetectable Firearms Act.

Democratic Sen. Chuck Schumer of New York attempted to add language to the ban to close what he called a "glaring loophole" in the law.

Sen. Chris Murphy, D-Conn., pushes for an extension of the Undetectable Firearms Act and reflects on the shootings at Sandy Hook Elementary School in Newtown.

Schumer argued that gun makers can meet the current requirements of the law by including a metal part that is easily detached, and he said the current ban fails to adequately address 3-D printing technology that could allow individuals to easily remove parts and carry undetectable guns through security checkpoints.

The new technology also raises fears that people could make gun parts that don’t register alarm when they pass through an X-ray machine – but could be assembled into a working gun after the screening.

But Schumer's efforts faced opposition from the gun lobby, including the National Rifle Association and Gun Owners of America. His proposed amendment did not receive a vote.

Before the measure passed, Schumer said the 10-year extension of the ban is "better than nothing, but it doesn't get us across the finish line."

"There is no sense in having this kind of threat to the safety of our people and the national security of this country," said Sen. Bill Nelson, D-Fla., in a press conference with Schumer after the law's passage.

The quiet nixing of additional restrictions was the latest defeat for gun control proponents, who have been unable to pass any new gun restrictions through Congress even after a massive push for new legislation in the wake of the Sandy Hook shooting.

While the powerful NRA did not oppose extending the ban as-is, the group lobbied against tightening its restrictions.

“We would like to make our position clear,” the group said in a statement last week. “The NRA strongly opposes ANY expansion of the Undetectable Firearms Act, including applying the UFA to magazines, gun parts, or the development of new technologies. The NRA has been working for months to thwart expansion of the UFA by Senator Chuck Schumer and others.”

The group Gun Owners of America also argued that the law’s language – and any additions proposed by Schumer – is too broad and could be used to justify additional restrictions on gun ownership.

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