Most responses to your original question try much too hard to complicate the issue. The first response was the best. If it is not specifically prohibited by the FAR's, then it is allowed by the FAA, period, end of statement. Now, whether or not it is allowed by the country and/or license where you are operating said aircraft becomes the jurisdiction of that individual CAA. In other words, you have to comply with the rules of both countries.
Last summer I was flying for a Swedish company, with my JAA/EASA license, on a wet-lease in Chile. We had to comply with EU Ops 1, AND DGAC rules. Usually EU Ops 1 was more restrictive, but not always. When it came to night flying, the DGAC rules were much more limiting.
Another example that applies directly to me right now, albeit with a different twist - Currently I am working for Embraer, a Brazilian aircraft manufacturer, in the United States, with my FAA license. Often our demo aircraft are PT registered. While operating said aircraft strictly within US airspace, the FAR's allow me to do so if I have an appropriate FAA license and type-rating. However, ANAC's rules do not allow this for commercial operations. More specifically, one must be a Brazilian citizen to fly for hire on an aircraft of Brazilian registry. SOoooo, whenever I fly a PT registered aircraft, my name doesn't even go into the ship's log. Since I am currently flying the Phenoms, which are single-pilot certified, I am technically (per ANAC) not even part of the crew, though per our company norms I am. Obviously this "work around" would not even be possible if I were currently flying an aircraft that requires two rated pilots...