Gillett v. Bullard was a United States Supreme Court case that addressed the issue of whether a state court had the authority to issue an injunction against a federal court. The case involved a dispute between two parties over a contract for the sale of a steamboat. The state court had issued an injunction against the federal court, preventing it from enforcing the contract. The Supreme Court held that the state court did not have the authority to issue an injunction against a federal court. The Court reasoned that the state court was not a court of competent jurisdiction to issue such an injunction, and that the federal court had exclusive jurisdiction over the matter. The Court also noted that the state court had no authority to interfere with the proceedings of the federal court. The Court concluded that the state court's injunction was invalid and that the federal court had exclusive jurisdiction over the matter. This decision established the principle that state courts do not have the authority to issue injunctions against federal courts.

Justice Field delivered the dissenting opinion in this case. He argued that the court should not have granted a writ of error to review the decision of the Supreme Court of California, as it was based on an interpretation and application of state law rather than federal law. The majority had held that Gillette's patent for his safety razor was valid and infringed upon by Bullard's product, but Justice Field disagreed with their reasoning. He believed that there were errors in both fact-finding and legal conclusions made by the lower court which should be corrected before any further action could be taken against Bullard. Furthermore, he argued that even if all facts found were correct, they did not necessarily lead to a conclusion about infringement or validity under federal patent laws; instead such questions must be determined according to state laws governing patents at issue. Therefore, he concluded that no writ of error should have been issued since there was no substantial question involving federal law presented for review by this case.