In the case of Commissioners of Santa Fe County v. Territory of New Mexico ex rel. Coler (1909), the U.S Supreme Court ruled on a dispute over tax assessments in Santa Fe County, New Mexico. The county commissioners had refused to levy taxes based on an assessment made by a territorial board, arguing that it was not their duty to do so under existing laws and that they were only required to levy taxes based on assessments made by county assessors. However, the court disagreed with this interpretation and held that it was indeed within the power and responsibility of the territorial board to make such assessments for taxation purposes. Therefore, it ordered Santa Fe County's commissioners to comply with these assessments when levying taxes.

In the dissenting opinion for Commissioners of Santa Fe County v. Territory of New Mexico Ex Rel. Coler, Justice Harlan disagreed with the majority's decision to uphold a tax assessment on railroad property by local authorities in New Mexico. He argued that this was not just an issue of state taxation but also involved federal jurisdiction because it concerned interstate commerce and thus fell under Congress' purview according to the Constitution's Commerce Clause. Harlan contended that railroads were instrumentalities of interstate commerce and should be protected from excessive or discriminatory state taxation which could interfere with their operation or burden interstate trade. He believed that allowing states such broad taxing power over these entities would undermine national unity and economic integration, leading potentially to commercial warfare among states as they competed for revenue at each other’s expense.