Laws generally come from legislatures.
When I unearth whatever newsletter I saw it in, I'll post the text. I'm pretty sure it was either on the Celebrity website or in the CC newsletter. It says that starting shortly it will be necessary to have all this info on file in advance--I forget how long in advance, maybe a week or two.
That's one reason they're pushing everybody to prefile online. As far as tickets themselves, the day is fast approaching when that piece of paper won't amount to a hill of beans. It'll all be based on what's in the computer and your passport or other official ID, just like at the airlines.
I know you feel that nothing's a law unless you know about it, but apparently this is some provision of one the blizzard of homeland security measures.
And, contrary to your belief, most if not all major cruise lines already make it possible for you to submit this info online as soon as your reservation is set up in the computer. For the cyber-challenged, they still let you submit paper versions, but you have to do it in advance. Apparently if you don't it is (or will be) a deal breaker.
As I say, when I find the reference again, I'll post it.