The leading case in the UK is Page v. Hull University I/uitor ([l993] l All ER. 97). It was held that Parliament had only conferred the decision making power on the basis that it was to be exercised on the correct legal basis: a misdirection in law in making the decision therefore rendered the decision ultra viler. ln general therefore, any error of law made by an administrative tribunal or inferior court in reaching its decision would be quashed for error of law. The seminal modern case on this topic in the United States is Chevron, US.A., Inc. v. Natural Resources Defense Council, Inc. (467 US S37(1984)). The case concerned the legality of regulations made pursuant to the clean air legislation. The Clean Air Act Amendments of 1977 imposed certain requirements on states that had not met the national air quality standards established by the Environmental Protection Agency(EPA). The requirements included an obligation on such states to establish regulatory regimes under which permits would be issued relating to ‘new or modified major stationary sources’ of air pollution. A permit could not be issued unless stringent conditions had been met. The EPA promulgated regulations designed to implement the permit requirement and these regulations allowed a state to adopt a plant-wide definition of stationary source. The effect of this was that an existing plant which had a number of pollution emitting devices could install or modify one piece of equipment without meeting the permit conditions, provided that the alteration did not increase the total emissions from the plant. The state was, therefore, allowed to treat all the pollution emitting devices within the same industrial grouping as though they were encased in a ‘bubble’. It was this constriction of the enabling legislation which was challenged by the National Resources Defense Council, the argument being that this interpretation was too generous to industrial users.