A new decision by the U.S. Court of Appeals for the Federal Circuit imposes significant limits on the use of the doctrine of equivalents to protect patents. Although the court majority said it was helping to preserve the function of patent claims as a notice to the public about what a patent actually covers, at least two of the justices warned that the ruling could severely limit the scope of protection for certain biotech patents.

At the very least, intellectual property attorneys expect the ruling to remake the playing field for both the prosecution and litigation of patents.