In the 1993 case of MCI Telecommunications Corporation v. American Telephone and Telegraph Company, the Supreme Court ruled in favor of AT&T. The dispute centered around whether or not MCI was allowed to offer long-distance telephone services without filing tariffs with the Federal Communications Commission (FCC). According to FCC regulations, all common carriers were required to file tariffs detailing their charges for interstate communication services. However, MCI argued that it should be exempt from this requirement because it did not qualify as a "common carrier" under FCC's definition due to its provision of specialized rather than general services. The court disagreed with this interpretation and held that any company providing communication channels between customers is considered a common carrier regardless of how specialized their service may be. Therefore, they concluded that MCI was indeed subject to tariff-filing requirements set by FCC regulations.

In the dissenting opinion for MCI Telecommunications Corporation v. American Telephone and Telegraph Company, Justice Scalia disagreed with the majority's interpretation of the term "modify" in Section 203(b) of Communications Act. He argued that this term should be understood to include both minor and major changes, contrary to the majority's view that it only allows minor alterations. According to him, if Congress had intended such a narrow definition, they would have used more specific language in drafting legislation. Furthermore, he criticized FCC’s decision as arbitrary because it granted MCI permission without considering AT&T’s objections or providing sufficient reasons for its approval. He also expressed concern about potential negative impacts on competition due to FCC’s broad authority over telecommunications industry under this ruling.