35 U.S.C. 102(d) – A person shall be entitled to a patent unless (d) the invention was first patented or caused to be patented, or was the subject of an inventorâ€™s certificate, by the applicant or his legal representatives or assigns in a foreign country prior to the date of the application for patent in this country on an application for patent or inventorâ€™s certificate filed more than twelve months before the filing of the application in the United States.
To qualify as a reference under 35 USC 102(d), a foreign application that has matured into a foreign patent. Barred from obtaining a patent if (all are yes):
1) Filed more than one year (12 months) before the effective filing date of the US application;
2) Filed by the same applicant, or his legal assigns, as the US application;
3) Issued as a patent or inventorâ€™s certificate before the filing of an application in the US (the patent rights granted must be enforceable, but need not be published); and
4) Involves the same invention.