How is it possible that such a ridiculous law can be enforced country
wide in the United States?

BRBR

Probably it can't. So go ahead and propagate (plants I mean) just don't put
the info on a billboad. It's like the opium poppy issue, in a way--I've seen
them all over California, but they're quite legal to grow as long as you don't
use them to make opium.

Now to chase those dragons out...
zemedelec