>also: how are they going to determine that you did?

Same as any crime. They have to prove that you did it (both that you did the act, and that you intended to do the act) to a judge or a jury beyond a reasonable doubt.

...after taking your hardware and placing you under house arrest for a time, then putting you under a gag order (national security) while simultaneously setting up preventative monitoring of future VPN use, until the case resolves.