Well, they may have a point. Was the sovereign citizen travelling on their own road or someone else's road whom gave them permission to? If so, that's totally fine and the police officer shouldn't be policing stuff owned by other people, only the government's stuff.
Oh, what's that? It was the government's stuff? Well, what a surprise. A person using roads that aren't their's and are in no position to pay for breaking anything or anyone while on them. It's like a stranger walking in your house and just using your shit, "It's okay, I'm a sovereign citizen and the law says I don't have to follow the law."
