In the case of State of South Carolina v. State of North Carolina (2009), the dispute revolved around water rights in the Catawba River, which flows through both states. South Carolina sued North Carolina alleging that it was allowing excessive withdrawals from the river, thereby violating its downstream neighbor's equitable apportionment rights to shared interstate waters. The Supreme Court appointed a Special Master to make recommendations on motions filed by several entities seeking to intervene in this original jurisdiction proceeding. The Special Master recommended granting intervention as parties for two cities and one utility company located upstream in North Carolina but denied intervention for Duke Energy Carolinas, LLC and an environmental group called Catawba Riverkeeper Foundation Inc., who sought participation as amici curiae instead. In a 5-4 decision, the Supreme Court upheld these recommendations with Justice Alito writing for majority opinion while Justice Thomas wrote dissenting opinion arguing against broadening scope of interventions.

In the dissenting opinion for the case of State of South Carolina v. State of North Carolina, Justice Antonin Scalia disagreed with the majority's decision to allow non-state entities to intervene in original jurisdiction disputes between states. He argued that this was a departure from historical precedent and could lead to complications in future cases. According to Scalia, only sovereign entities should be allowed as parties in such disputes because they alone have an interest independent of their citizens' interests which is what interstate controversies are about - not resolving private rights but preventing or remedying injuries among states themselves. The justice also expressed concern that allowing intervention by non-state actors would turn these types of cases into multi-party litigations where each party seeks its own advantage rather than focusing on resolving issues between states.