In the case of Kenneth Cory, Leo T. McCarthy and Jesse R. Huff v. Western Oil and Gas Association et al., 1984, the U.S Supreme Court was asked to decide on a dispute regarding California's method of taxing oil and gas reserves within its borders. The state had implemented a system that taxed these resources based on their future value rather than their current worth, which led to higher tax rates for companies in this industry compared to other businesses in California. The Western Oil and Gas Association challenged this taxation method as unconstitutional under the Equal Protection Clause because it resulted in discriminatory treatment against them. The Supreme Court ruled in favor of the State officials (Cory, McCarthy & Huff), upholding California’s right to levy taxes based on anticipated future values of oil and gas reserves instead of present market value at extraction point - known as "reserve taxation". It found no violation with respect to either Due Process or Commerce Clauses since there was no evidence showing that such tax structure would lead directly or indirectly towards any form of discrimination between interstate commerce activities.

In the dissenting opinion for Cory v. Western Oil and Gas Association, Justice O'Connor disagreed with the majority's decision that California's method of taxing oil and gas reserves was not discriminatory against interstate commerce. She argued that the state's tax system did discriminate because it taxed out-of-state companies at a higher rate than in-state ones due to its use of current market value rather than acquisition cost as a basis for taxation. This resulted in an unfair burden on interstate commerce, violating the Commerce Clause of the Constitution. Furthermore, she contended that this case should have been evaluated under Complete Auto Transit Inc., v Brady’s four-part test which determines whether a state tax violates this clause or not; instead, it was assessed using an outdated standard from another case (Spector Motor Service Inc., v O’Connor). The justice also noted inconsistencies between how different types of property were valued within California itself - some based on purchase price while others used current market value - further evidencing discrimination within their taxation system.