They weren't, but most of the laws put in place directly because of 9/11 have nothing to do with preventing anything that had happened or that will happen.

Companies have the right to do whatever they please which includes making each customer show ID or not as long as they are a privately owned business. Which is perfectly fine, I'd rather not have the government have a hand in businesses anyway. But stating it's the law is a falacy and is misleading to their customers.

Whether you think it's right or wrong, you can't deny ID-ing people is a practical and smart business move.
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Freedom is the freedom to say that two plus two make four. If that is granted, all else follows.
-George Orwell