Well, I'd be very
surprised (and pleased) if there were a law enforcing spelling
You could threaten people who write very very sloppily in, say, a forum, with a charge. Wouldn't that be absolutely nice sometimes?
Now, honestly, of course it's not enforced on the people to write like the spelling reform tells you to write. In fact, nobody even forces you to write like how they told you in school before the spelling reform. These are guidelines, and should be followed so that you have a common ground with the people you are trying to communicate with.
Back in the middle ages, they had no such guidelines and everyone (well, those who actually could write) wrote just like they wanted. It _worked_, and even today you can more or less understand the texts they wrote back then, but it certainly wasn't very nice
Now, despite not being enforced in any way, the new spelling rules will eventually spread out and become what most of the people use, simply because the young people all learn the new rules and the old people (eventually) die out.
I'd like to compare this to, say, a new version of a programming language, where some old functions have been marked as "deprecated" and are only kept for backwards compatibility and you're strongly discouraged to use them in new programs you write. I think it's pretty much the same thing..