Argument for what?<p>Someone would need to propose a specific law. A law that says &#x27;you may only contract with [insert privileged electronic currency here]&quot; or something similar.<p>If the enforcement is through confiscation of other currencies it will likely violate 4th amendment protections on personal effects.<p>If certain contracts are banned (instead of, or in addition to, confiscation) it would violate speech protections. Exchanging money (in any form) is speech, as are your contractual dealings.