The US Supreme Court may be about to rewrite some of the most fundamental rules of innovation in America, as it considers a handful of cases that could change the course of US intellectual property law and undermine the value of patents owned by domestic and foreign companies. Congress has been struggling for months to write a new law that would reform the country's patent system, which has been criticised for granting too many, often poor-quality, patents, and for encouraging ruinously costly litigation. But legislative attempts at reform appear to have foundered, so attention has turned to the Supreme Court to create a better balance between competition and innovation. The court has three cases before it and a fourth that could arrive soon, which test some of the most fundamental tenets of US patent jurisprudence. Which country's courts should decide patent disputes that cross borders? And even more fundamentally, What can be patented in the first place? How obvious must an invention be to forfeit patent protection? And should challengers in patent infringement suits – even those who are not using the patent to produce anything – be allowed to shut down defendants whose products depend on many patents?