The Protector was a Supreme Court case from 1870 that dealt with the issue of whether a patent for a steamboat was valid. The patent was granted to the inventor, John Fitch, in 1791. The case was brought by the heirs of Fitch, who argued that the patent was still valid and should be enforced. The Supreme Court ultimately ruled in favor of the heirs, finding that the patent was valid and enforceable. The Court reasoned that the patent was valid because it was issued before the Patent Act of 1793, which established the modern patent system. The Court also found that the patent was valid because it was issued before the invention of the steamboat, which was not invented until 1807. The Court also noted that the patent was issued before the invention of the steam engine, which was not invented until 1816. The Court's ruling was significant because it established that patents issued before the Patent Act of 1793 were still valid and enforceable. This ruling has been cited in numerous subsequent cases and has been used to support the validity of patents issued before the modern patent system was established.

In The Protector, the Supreme Court was tasked with determining whether a patent for an invention of a machine used to make paper bags could be granted. Justice Field delivered the dissenting opinion in which he argued that while Congress had authority to grant patents on inventions, it did not have power to grant exclusive rights over machines already known and used by others prior to the application. He further argued that granting such exclusive rights would amount to taking away property from those who had previously been using them without compensation. In conclusion, Justice Field believed that if Congress wanted inventors of existing machines or processes protected they should pass laws providing for their protection rather than relying on patent law as it existed at the time.