The U.S. is apparently not happy with the government of Pakistan. It appears that they have taken Harpoon anti-ship missiles and have allegedly been modifying them for use against land targets. Something that would threaten India. The Pakistani government denies this and claims that the missiles they have been testing are homegrown and possibly only partly based on the Harpoon missiles that the U.S. government sold to them during the Reagan years.
None of this really matters of course, if the U.S. sold them the missiles then Pakistan should be able to do whatever they want with them. In the future, perhaps the our government can be a little bit more careful when deciding who to sell weapon systems to.
I wouldn’t expect to be able to sell missiles, guns, or bombers to a sovereign country and then expect them to never modify or improve them. The fact that our government is now complaining about this is just silly. To the best of my knowledge, there is no “fair use” clause for missile technology. Even if there is, good luck on enforcing that copyright law.