The Supreme Court on Monday tightened restrictions on gun purchases, ruling that the government can be strict in trying to weed out potential “straw” buyers who plan to traffic the weapons.

The 5-4 ruling, which saw court’s four Democrat-appointed justices joined by Justice Anthony M. Kennedy in what was seen as the biggest test of gun rights during this term. The majority signaled their desire to strictly interpret gun laws when it comes to background checks.

“No piece of information is more important under federal firearms law than the identity of a gun’s purchaser — the person who acquires a gun as a result of a transaction with a licensed dealer,” Justice Elena Kagan wrote in the majority opinion.

The case involved a former police officer who thought he could get a discount on guns, and offered to buy one for his uncle. Bruce Abramski Jr. bought a Glock 19 and listed himself as the buyer, clearing a federal background check. He then transferred the gun to his uncle, again done through a federally licensed dealer, clearing a background check in compliance with state law.

But federal authorities said that violated the law, since he wasn’t the true purchaser.

The ruling doesn’t strike at the heart of the Second Amendment’s right to bear arms, but it does signal an interest on the part of justices to make sure the laws Congress has written governing background checks are interpreted strictly.

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