US patent law only covers US patents. However, several aspects of US patent law can have global affects and implications.
Under 35 U.S.C. §271, patent infringement is committed by whoever:
without authority makes, uses, offers to sell, or sells any patented invention, within the United States, or imports into the United States any patented invention during the term of the patent therefor…
The path toward “importing” obviously starts with manufacturing outside the US. That manufacturing won’t violate US patent law, but the importing will.
US patent law also prohibits importing into the US something made by a process protected by a US patent, as set forth in 35 U.S.C. §271(g):
Whoever without authority imports into the United States or offers to sell, sells, or uses within the United States a product which is made by a process patented in the United States shall be liable as an infringer, if the importation, offer to sell, sale, or use of the product occurs during the term of such process patent.
Whether foreign sales can be taken into account when considering damages for infringement of US patents is somewhat complicated.
In the 2013 case of Power Integrations Inc. v. Fairchild Semiconductor International Inc., the Federal Circuit held that a jury’s award of $33 million for patent infringement damages, based on worldwide sales of the infringing products, was contrary to law:
the entirely extraterritorial production, use, or sale of an invention patented in the United States is an independent, intervening act that, under almost all circumstances, cuts off the chain of causation initiated by an act of domestic infringement.
However, in a recent decision in Carnegie Mellon Univ. v. Marvell Tech. Grp. Ltd., as reported by Reuters,
In a 3-0 vote, the U.S. Court of Appeals for the Federal Circuit on Tuesday said Marvell must pay at least $278.4 million, representing a 50-cent-a-chip royalty on 556.8 million chips imported into the United States for use in the drives.
The court ordered a new trial to determine the extent to which Marvell chips made abroad and not imported may ultimately have been the subject of a domestic “sale,” justifying higher royalties for Pittsburgh-based Carnegie Mellon.
This is just a very brief sample of the types of patent law issues involved when patented products cross international borders.