Just the laws that aren't also supported by the reasonable working of a just society. Murder and theft are wrong because they hurt people. Not keeping kosher isn't illegal here because if you eat bacon, the only person you hurt is yourself...unless you count the pig.
Keeping kosher isn't the law because the majority of people like to eat pork. If the majority thought that pork was unclean and should not be consumed under any circumstances, there is nothing in our laws that would stop such laws from being passed. I suspect they would pass constitutional muster as well; no one's rights are being infringed.
The harm or lack of harm a thing does has precious little to do with its legality. The only thing stopping us from making eating pork illegal is that most people like to eat it.