This is certainly a surprise. I suppose they're actually starting to worry about their credibility:

WASHINGTON — The Supreme Court dealt a rare blow to the gun lobby Monday by ruling that purchasers must report when they are buying firearms for other people.

The 5-4 decision upheld two lower courts that had ruled against so-called straw purchasers, even though the justices acknowledged that Congress left loopholes in gun control laws passed in the 1960s and 1990s.

For gun purchasers to be allowed to buy from licensed dealers without reporting the actual final owners of the firearms, the justices said, would make little sense.

"Putting true numbskulls to one side, anyone purchasing a gun for criminal purposes would avoid leaving a paper trail by the simple expedient of hiring a straw," Justice Elena Kagan wrote for the slim majority.

Kagan, a New Yorker who acknowledged during her 2010 confirmation hearings that she was not very familiar with guns, was opposed by four conservative justices, led by Justice Antonin Scalia -- who famously has taken her hunting on several occasions.

"No piece of information is more important under federal firearms law than the identiry of a gun's purchaser -- the person who acquires a gun as a result of a transaction with a licensed dealer," Kagan said.

During oral arguments in the case in January, she had noted that without such a finding, "it does not matter whether the ultimate transferee was Al Capone or somebody else."

Scalia's dissent for the court's conservatives -- not including Justice Anthony Kennedy, who provided the swing vote -- was scathing.

"The court makes it a federal crime for one lawful gun owner to buy a gun for another lawful gun owner," he said. "Whether or not that is a sensible result, the statutes Congress enacted do not support it."

[...] Gun control advocates were delighted. "This is a very big and very positive decision that will save lives by keeping guns out of the hands of dangerous people," said Dan Gross, president of the Brady Center to Prevent Gun Violence.

It was the second ruling from the conservative court this term that went against the gun lobby. In March, the justices ruled unanimously that a federal law intended to keep guns away from domestic violence offenders can apply even if their crime was nothing more than "offensive touching."