The U.S. Supreme Court case Maislin Industries, U.S., Inc., et al. v. Primary Steel, Inc., et al in 1989 revolved around the issue of whether a carrier could collect undercharges from a shipper after providing services at discounted rates agreed upon by both parties but not filed with the Interstate Commerce Commission (ICC). The ICC had previously ruled that carriers were obligated to charge and shippers to pay no more than the tariff rates on file with them, even if they had negotiated lower prices privately. However, this decision was challenged by Maislin Industries who argued that it violated their right to make contracts freely without government interference. In its ruling, the Supreme Court sided with Maislin Industries stating that while Congress did give authority to ICC for regulating tariffs and preventing discriminatory practices among carriers; it didn't grant power over private agreements between shippers and carriers regarding pricing or allow for retroactive billing adjustments based on unfiled tariffs. This landmark judgement clarified legal boundaries within which shipping companies can operate when negotiating service fees outside of those listed in public tariffs filed with regulatory bodies like ICC thereby protecting businesses from unexpected financial liabilities due to regulatory interventions.

In the dissenting opinion of Maislin Industries, U.S., Inc. v. Primary Steel, Inc., Justice Blackmun argued that the majority's decision undermined the Interstate Commerce Commission's (ICC) authority to regulate and interpret laws related to transportation rates in interstate commerce. He contended that Congress had granted ICC broad discretion over these matters and it was not for courts to interfere with this power unless there were compelling reasons or clear statutory violations involved. The justice believed that by allowing carriers like Maislin Industries to charge customers more than their filed rates without prior approval from ICC, as per its 'negotiated rates policy', would lead to discriminatory practices against certain shippers and destabilize rate structures across industries - something which he thought was contrary to public interest and legislative intent behind relevant statutes such as Motor Carrier Act of 1980.