Implied licenses may arise by operation of law from actions by the licensor which lead the licensee to believe that it has the necessary permission.
In reality, there is a continuum between these kinds of implied license and it may be difficult to determine whether the license or contract in question is one which the law implies, irrespective of any protests by the unwilling licensor, or instead one inferred from the whole pattern of factual circumstances including the evidence of intent.
[citation needed] In England, there is more of a tendency to regard all implied licenses as matters of fact and intent, while what would be a license implied by law in the US is treated under some other branch of substantive law such as the doctrine of non-derogation from grants.
[10] In both countries, the exhaustion doctrine has the effect of creating an implied license to use a product sold under the "authority" of the patentee.
It is controversial whether and to what extent contractual expedients can successfully limit the scope of such implied licenses.