In the 1910 case of Moffitt v. Kelly, Treasurer of Alameda County, California, the U.S Supreme Court dealt with a dispute over property tax assessments. The plaintiff, Moffitt, argued that his properties were unfairly assessed at full value while other properties in Alameda County were undervalued for taxation purposes. He claimed this violated the Equal Protection Clause of the Fourteenth Amendment and sought to prevent collection of taxes based on these assessments. However, the court ruled against him stating that it was not within its jurisdiction to interfere with state tax laws unless there is clear violation or transgression beyond debate which wasn't evident in this case. It held that minor discrepancies in assessment values did not constitute such a violation as long as they weren't intentional or systematic discrimination by assessors.

The dissenting opinion in the case of Moffitt v. Kelly, Treasurer of Alameda County, California argued that the majority's decision to uphold a tax on mortgages was incorrect. The dissent contended that this tax was essentially a double taxation because it taxed both the property and its mortgage separately. They believed this violated principles of equity and fairness in taxation as well as constitutional protections against such practices. Furthermore, they disagreed with the majority's interpretation of previous court rulings on similar issues, arguing these precedents did not support taxing mortgages independently from their associated properties. Overall, they felt that allowing such taxes would unjustly burden property owners who chose or needed to finance their purchases through mortgages.