In the case of Phillips Chemical Co. v. Dumas Independent School District, the Supreme Court ruled in favor of Phillips Chemical Co., stating that a Texas law allowing school districts to tax intangible property was unconstitutional under the Fourteenth Amendment's Equal Protection Clause. The company had been taxed on its sulfur rights by two different entities: Moore County and Dumas Independent School District (DISD). While Moore County assessed taxes based on physical assets like buildings and equipment, DISD also included intangible assets such as mineral rights in their assessment. The court found this double taxation unfair and discriminatory against companies with significant intangible properties compared to those without such holdings.

In the dissenting opinion for Phillips Chemical Co. v. Dumas Independent School District, Justice Brennan argued that the Court's decision to uphold a Texas statute allowing school districts to tax property located within their boundaries but owned by federal contractors was incorrect and inconsistent with previous rulings. He contended that this ruling effectively allowed states to impose taxes on federal property, which is constitutionally prohibited under the Supremacy Clause of Article VI. Furthermore, he asserted that such taxation could potentially interfere with federal activities and operations as it might discourage private entities from contracting with the government due to increased financial burdens imposed by state taxation laws. Therefore, in his view, this case should have been decided in favor of Phillips Chemical Company rather than Dumas Independent School District.