Wollensak v. Reiher was a United States Supreme Court case that dealt with the issue of whether a patentee could sue for infringement of a patent after the patent had expired. The plaintiff, Wollensak, had obtained a patent for a machine for making paper bags. After the patent expired, Reiher began making and selling a similar machine. Wollensak sued Reiher for patent infringement. The Supreme Court held that a patentee could not sue for infringement of a patent after the patent had expired. The Court reasoned that the patentee had already received the benefit of the patent, which was the exclusive right to make, use, and sell the invention for the duration of the patent. Once the patent expired, the patentee no longer had any exclusive rights and could not sue for infringement. The Court also noted that allowing a patentee to sue for infringement after the patent had expired would be unfair to the infringer, who would be liable for damages even though the patentee had already received the benefit of the patent. In conclusion, the Supreme Court held that a patentee could not sue for infringement of a patent after the patent had expired. The Court reasoned that the patentee had already received the benefit of the patent and that allowing a patentee to sue for infringement after the patent had expired would be unfair to the infringer.

In Wollensak v. Reiher, the United States Supreme Court was tasked with determining whether a patent for an invention of a machine used to make paper bags could be extended beyond its original term due to delays in the Patent Office caused by the Civil War. The majority opinion held that no extension should be granted because Congress had not provided any authority for such extensions and it would set a dangerous precedent if they did so without explicit authorization from Congress. Justice Field dissented, arguing that while there may have been no express statutory provision allowing for extensions of patents due to delays in processing applications at the Patent Office, this was nevertheless within their power as part of their duty under Article III Section 2 of the Constitution which grants them jurisdiction over all cases arising under federal laws relating to patents and copyrights. He further argued that since Congress had taken steps during Reconstruction following the Civil War which allowed certain other claims against government agencies or officers who were negligent or delayed action on matters related to war-time activities, then surely they must also allow some form of relief when similar negligence occurred at one of their own offices like the Patent Office.