The commission shall establish priorities among the types or categories of customers of every electrical corporation and every gas corporation, and among the uses of electricity or gas by such customers. The commission shall determine which of such customers and uses provide the most important public benefits and serve the greatest public need and shall categorize all other customers and uses in order of descending priority based upon these standards. The commission shall establish no such priority after the effective date of this chapter which would cause any reduction in the transmission of gas to California pursuant to any federal rule, order, or

regulation.