GE’s attempt this week to keep Siemens Gamesa out of the US market, by brandishing a patent which should have long since expired may well backfire, if Siemens Gamesa challenges the validity of the patent, which is more than 20 years old. Chances are it will threaten this in talks, but then settle for some payment to GE and then get on with US business. US patent cases are notorious for “home court decisions” and Apple versus Samsung was a famous one where Apple tried to patent both look and feel of a device which, although designed to look similar at rest, behaved entirely differently when used; and tried to patent simple ideas like “pinch to zoom on a phone…