I have no idea what Uganda's copyright laws are, but in a civilized state no one, not even the president, can copyright traditional material and make it stick, if someone with half a brain and a lawyer with at least the complementary other half is willing to challenge it in court. Provided, of course, that there is solid documentation that the material in question actually preexisted the copyright claim(ant). Now, it's possible that the president created new lyrics to a traditional tune, in which case he could copyright the former (and in fact in the US and probably Uganda would automatically have common-law ownership of them), but not the latter. The distinction between text and tune is often lost on commentators, singers, publishers, etc.

Haruo