라이선시 금반언에 관한 미국 특허판례의 동향

In the early court precedents in the United States, the courts had recognized the estoppel doctrine in patent licensing and transfer agreement. However after the Supreme Court of the United States denied the doctrine of licensee estoppel in the Lear case of 1969 as a public policy for the elimination of an improper patent, the courts continued to maintain such attitude as was evident in the latest MedImmune case in 2007. With the doctrine of assignor estoppel however, the U.S. court decisions had generally accepted the doctrine of assignor estoppel in present as well as it was in the past. A negative attitudes towards the doctrine of assignor estoppel had once been shown in the obiter dicta of the Lear case of the Supreme Court of the United States in 1969, and this was immediately repeated in the lower court decisions. However, assignor estoppel has revived and is still maintained since the Court of Appeals for the Federal Circuit of the United States (CAFC) once again recognized this doctrine in the Diamond Scientific case in 1988. Since then, the general contention is that the U.S. courts are in favor of the doctrine of assignor estoppel. The main reason why the doctrine of assignor estoppel is recognized as in contrast to the doctrine of licensee estoppel is that the assignor who would challenge the patent has already been fully paid for the patent rights, whereas the licensee might be forced to continuously pay for a potentially invalid patent. As regards to no-challenge clauses, the United States precedents shows that the validity or an enforceability of such clauses is generally denied. But with regard the no-challenge clauses that are included in the settlement agreements, United States precedents consider no-challenge clauses in pre-litigation settlement agreements as unenforceable while such clauses in post-filing settlement agreements as valid and enforceable.