One of the fairly explicit exceptions to federal jurisdiction on interstate travel is precisely to prevent the spread of diseases, both human and agricultural.

One of the fairly explicit exceptions to federal jurisdiction on interstate travel is precisely to prevent the spread of diseases, both human and agricultural. Agriculture inspections and quarantine type cost recovery are pretty much the only "taxes/tarrifs" the states are allowed to prescribe on interstate (and international) travel and trade. From US Constitution Article 1 Section 10: No State shall, without the Consent of the Congress, lay any Imposts or Duties on Imports or Exports, except what may be absolutely necessary for executing it's inspection Laws Like much of the US Constitution, it's both a very loaded and ambiguous statement, with much of it's meaning implied.