So last week, a three-judge panel of the US Fifth Circuit Court upheld a federal law that prohibited the sales of handguns to out-of-state residents. The main justification for their decision - after getting past all the legal gobbledygook - was that the federal law remains in the best interest of the public.
It's always depressing when our federal courts make decisions based on their own whims of what is or is not in the public interest rater than the clear limitations delineated by the Constitution. Humans can be very moody beasts and a judicial stomach ache caused by "an undigested bit of beef, a blot of mustard, a crumb of cheese, a fragment of an underdone potato." will often result in the production of copious amounts of "public interest".
I suppose part of the court's justification could be that while the Constitution protects the rights of citizens to keep and bear arms, it doesn't say diddly-squat about being able to buy them. Of course to be fair, it also doesn't say anything about being able to shoot them either, so I suppose you can have them and you can carry them but in the public interest you can't use them, purchase them, or sell them.
More often than not "public interest" is just another aphorism for "bovine excrement". But no matter which phrase you use, if it doesn't square with the laws of nature's God or the governmental limits of the Constitution, it has no place in jurisprudence.