The U.S. Supreme Court case Princess Lida of Thurn and Taxis et al. v. Thompson et al., Trustee, 1938 revolved around a dispute over jurisdiction between state and federal courts in matters related to trust administration. The plaintiff, Princess Lida of Thurn and Taxis, sought to remove the trustees appointed by Pennsylvania's Orphans' Court for her children's trusts due to alleged mismanagement. Simultaneously, she filed an action in Federal District Court against the same trustees seeking an accounting of their actions as fiduciaries under the trusts. The main issue was whether both suits could proceed concurrently without violating principles of comity or interfering with each other’s jurisdictions since they involved substantially similar issues and parties. The Supreme Court held that where two courts have concurrent jurisdiction over a matter - one being a state court exercising probate jurisdiction (Orphans’ court) while another is a federal court operating under diversity jurisdiction (District court), if proceedings are first commenced in one forum then it should be allowed exclusive control until its work is completed.

In the dissenting opinion for Princess Lida of Thurn and Taxis et al. v. Thompson et al., Trustee, Justice Black argued that the federal court should have abstained from exercising jurisdiction over a dispute already being litigated in state court. He contended that principles of comity and respect for state judicial proceedings necessitated such restraint, especially given that both cases involved essentially the same parties and issues. Furthermore, he warned against potential conflicts between federal and state courts which could arise if both were allowed to proceed simultaneously with their respective cases. In his view, this risked undermining public confidence in the judiciary as well as causing unnecessary confusion among litigants about where they should bring their claims.