Blonder–Tongue Doctrine Law and Legal Definition

In relation to Patent law, the blonder-tongue rule states that a patentee is precluded by collateral estoppel from relitigating the validity of a patent that has been held invalid early. According to this doctrine, a patentee is barred from relitigating, only if, in a prior suit such patentee had a full and fair opportunity to litigate the patent’s validity.