In the settlement of a lawsuit, GM paid Elwell an undisclosed sum of money, and the parties agreed to a permanent injunction. The injunction prohibited Elwell from 'testifying, without the prior written consent of [GM], . . . as . . . a witness of any kind . . . in any litigation already filed, or to be filed in the future, involving [GM] as an owner, seller, manufacturer and/or designer . . . .' GM separately agreed, however, that if Elwell were ordered to testify by a court or other tribunal, such testimony would not be actionable as a violation of the Michigan court's injunction or the GM-Elwell agreement. Elwell was subpoenaed to testify in a product liability action commenced in Missouri by plaintiffs who were not involved in the Michigan case. The decedent, Beverly Garner, was a front-seat passenger in a 1985 Chevrolet S-10 Blazer involved in a February 1990 Missouri highway accident. The Blazer's engine caught fire, and both driver and passenger died. In September 1991, Garner's sons, Kenneth and Steven Baker, commenced a wrongful death product liability action against GM in a Missouri state court. The Bakers alleged that a faulty fuel pump in the 1985 Blazer caused the engine fire that killed their mother. GM removed the case to federal court on the basis of the parties' diverse citizenship. On the merits, GM asserted that the fuel pump was neither faulty nor the cause of the fire and that collision impact injuries alone caused Garner's death. The Bakers sought both to depose Elwell and to call him as a witness at trial. GM objected to Elwell's appearance as a deponent or trial witness on the ground that the Michigan injunction barred his testimony. In response, the Bakers urged that the Michigan injunction did not override a Missouri subpoena for Elwell's testimony. The Bakers further noted that, under the Elwell-GM settlement agreement, Elwell could testify if a court so ordered, and such testimony would not be actionable as a violation of the Michigan injunction. The court allowed the Bakers to depose Elwell and to call him as a witness at trial. The United States Court of Appeals for the Eighth Circuit reversed the District Court's judgment, ruling, inter alia, that Elwell's testimony should not have been admitted.