Actually NovaLogic tried to copyright the use of the F-22 in their Sim so that they could take other developers to Court for using the F-22 in other Sims.
Lockheed had to step in and stated that due to their work belonging to the U.S. Citizens (through use of the U.S. Military), no company had the right to exclusive use of any Military Hardware so any U.S. Developer that wanted to use any hardware could do so.
Now, using the likeness of any of the U.S. Branches is a different matter. And I do believe that's why there is no reference to the U.S. Navy anywhere in SH4.
As for buying copies of the U.S. Medals, why, you can legally buy any and all real U.S. Medals in many Military Surplus stores or here :
http://www.usmedals.com with the exception of the CMOH. So YES, the President can make laws (with the support of Congress). As it stand, even a CMOH that's stamped "COPY" on the back is now illegal to own or buy (thanks Clinton).