The U.S. Supreme Court case American Trucking Associations, Inc., et al. v. Scheiner, Secretary, Department of Revenue of Pennsylvania, et al., 1986 revolved around the constitutionality of Pennsylvania's tax scheme on commercial truckers operating within its borders. The plaintiffs - out-of-state trucking companies and associations - argued that these taxes violated the Commerce Clause by unfairly burdening interstate commerce and favoring in-state businesses. The disputed taxes included an annual flat fee for every truck registered in the state (regardless if it was used exclusively within or outside Pennsylvania) and a marker fee for trucks not based in Pennsylvania but using its highways. In a 7-2 decision, the Supreme Court ruled that both fees were unconstitutional as they discriminated against interstate commerce by imposing higher costs on out-of-state operators compared to their local counterparts for access to public highways – thus violating principles of fair apportionment under the Commerce Clause.

In the dissenting opinion for American Trucking Associations, Inc., et al. v. Scheiner, Secretary, Department of Revenue of Pennsylvania, et al., Justice O'Connor argued that the majority's decision was inconsistent with previous rulings on interstate commerce and taxation. She contended that Pennsylvania's flat tax did not discriminate against out-of-state businesses because it applied equally to all trucks using its highways regardless of their origin or destination. The justice also pointed out that this type of tax is necessary for states to maintain their infrastructure and provide services essential for commercial activities like trucking operations. Furthermore, she criticized the majority’s reliance on a balancing test which in her view should be used sparingly as it can lead to unpredictable results and undermine state sovereignty over local matters such as taxation.