This is federal law

Claims that 'this is federal law' are beginning to bug me. It seems like overkill, after all why not just tell people what you are allowed to do, and what you aren't, and leave it at that. If you're one of those disobedient buggers then 'federal law' or not I very much doubt it makes the slightest difference, and just makes them look like officious arses. Admittedly air travel is getting weirder every day (save for San Francisco, where they managed to mix it up a little and have a bit of a comedy routine: "no waters, gels, toothpaste; ladies, you are allowed your lipstick, guys, this is San Francisco, you are also allowed your lipstick…") and one feels less and less welcome, despite ever increasing travel prices.
Still, welcome to New York! Will let you know what it does.