Prohibits most favored nation clauses, or clauses having a similar effect, in an agreement between an insurance carrier and a participating provider. A most favored nations clause is an agreement between a payer (such as an insurance company) and a provider that typically requires a provider to give the payer the lowest rate that it gave to any other comparable payer, which can be anticompetitive by encouraging oligopolistic pricing by large payers and increasing barriers for new entrants.