One of the most important things to understand about intellectual property is that it is nation-specific. That is, if you have a Canadian patent for a particular invention, you cannot enforce that patent outside of Canada. You would not, for example, be able to enforce that patent in a German court. There are certain complications to this rule, including international patent organizations (like the European Patent Organization or the World Intellectual Property Organization) which grant patent rights enforceable in multiple member countries or establish legal structures that allow you to easily apply for patents in multiple countries for the same invention. In fact, it is the norm for corporations to file the same patent application in multiple countries (the United States, China, Japan, South Korea, the European Patent Organization, and Taiwan currently being the "big six") to obtain protection in all of their primary markets. But this much has always been the case: intellectual property has never been international.

Insofar as we are talking about, say, Britons being obliged to respect the German patents of corporations during World War Two, then, the answer to your question is a pretty simple "no." During wartime, just as during peacetime, there is no international applicability of intellectual property assets.

So far, so boring. Sorry. But this does raise an interesting, related issue: How are the domestic intellectual property rights of foreign entities treated during wartime? That is, if a German corporation held a U.S. patent, would U.S. corporations have been obliged to respect that patent during World War Two? This is a serious issue, because corporations have been developing "global" patent portfolios for almost as long as there have been patents. And these intellectual property rights - just like any other property rights - don't just disappear when two countries go to war. They do, however, lose virtually all of the force they might have on behalf of their original owners, because the possession of intellectual property is only meaningful to the extent that the owner is able to enforce the right. Owning a patent is as good as worthless if you cannot at least potentially go to a court to sue someone for infringing that patent. Such is, of course, the case when countries go to war. Citizens of Country A lose access to Country B, including its courts, and vice versa.

But the rights themselves are still there. A patent still exists, and has some potential value, even when it is cut off from its owner. What has happened to such patents has depended largely on the particular case, but confiscation is not uncommon. Take, for instance, the patents of German corporations in the United States during the World Wars. The Trading with the Enemy Act of 1917 gave America's Chief Executive expansive powers to impound, restrict, and confiscate the property of enemy nationals in times of war. German-held U.S. patents were one of the forms of property subject to confiscation by the Office of Alien Property Custodian, a sub-division of the United States' Department of Justice. In December of 1918, all of the American property of the Bayer Corporation (headquartered in Leverkusen, Germany, and a future member of the infamous chemical manufacturing conglomerate I.G. Farben) was auctioned off to an American corporation. One of the most galling aspects of the Versailles Treaty for German corporations was that these "impounded" patent rights were never to be returned. The same Office conducted a similar confiscation during the Second World War.