The U.S. Supreme Court case A.L. Mechling Barge Lines, Inc., et al. v. United States et al., 1961 centered around a dispute over the legality of long-term contracts between railroads and coal companies for transportation services at fixed rates lower than those published in tariffs filed with the Interstate Commerce Commission (ICC). The petitioners, barge lines operating on inland waterways, claimed these contracts were discriminatory and violated the Interstate Commerce Act because they offered preferential treatment to certain shippers by providing them with lower rates not available to others. The Supreme Court ruled in favor of the United States and upheld these long-term contracts as legal under federal law governing railroad rate practices. It held that such agreements did not constitute undue or unreasonable preference or advantage within meaning of ICC Act section 3(1), nor did they result in any unlawful discrimination against other shippers who didn't have similar arrangements. This decision was significant as it clarified how anti-discrimination provisions of federal transportation law applied to contractual relationships between carriers and their customers.

In the dissenting opinion for A. L. Mechling Barge Lines, Inc., et al. v United States et al., Justice Harlan argued that the majority's decision was based on a misunderstanding of the Interstate Commerce Act and its amendments. He contended that Congress intended to allow railroads to compete freely with other modes of transportation, including barge lines, without being subject to rate regulation unless there were specific findings of predatory pricing or discrimination against shippers who chose not to use their services. In his view, this case did not meet those criteria because it involved a voluntary agreement between a railroad and some shippers rather than an attempt by the railroad to force all shippers onto its own lines at unfair rates.