Yes, if you convinced a lot of people to transact in cans of beans, you would be undermining the control of the government. Just look at countries that don't have a (viable) currency. They are using dollars or euros and are subject to a foreign powers monetary policy.
Also no country defines sovereignty through voluntary consent. Laws applies to you whether you agree or not.
Also no country defines sovereignty through voluntary consent. Laws applies to you whether you agree or not.