Are there any rules about what spoken languages can be used in what circumstances? I can imagine a lot of local hobbyists in the US getting upset if a few peopl

Are there any rules about what spoken languages can be used in what circumstances? I can imagine a lot of local hobbyists in the US getting upset if a few people started speaking Spanish on the radio. What if people speak a language that very few people know? Unless there's some rule encouraging the use of language that is widely understood in the region, then it seems like encryption would only "cause" a problem because, well, crap, we're just accustomed to people using a language we can understand.