Like most criminal law the laws don’t care about how to implement detection. The laws only outline punishment.
A lot of laws are like this if you think about them.
They’re not going to snoop every computer but by blocking VPN software and firewalling their IPs they should stop most people. Then catching people becomes easier because those people need to take actions to illegally find a new VPN. heck the govt could set up a Brazilian honey pot.
But theoretically if you have access to the outside internet and enough money to set up arbitrary servers you can tunnel encrypted traffic without anyone knowing what it is.
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