I'm not an American so I don't know if this is possible but could not a lawyer start a class action using all the sovereign citizens as complainants against a credit card company on the basis that said company did not do their due diligence before issuing cards to people so unhinged they couldn't possibly have entered into a contract with someone that required informed consent?

I feel like putting these people on the stand for about five minutes each would give ample supporting evidence of the proposition.