While I am least opposed to generic disclosure requirements (as opposed to a requirement of getting the approval of and registering with some specific regulatory authority, as is the case with getting an exemption to the prohibition on offering securities to the public) like you describe, it is still a prohibition on what Mayweather can say.
The law essentially says, "you cannot say X, unless you say Y and Z". It is a prohibition on what he can say under particular conditions. That being said, I haven't fully considered the implications of disclosure requirements, and would hold it as a possibility that it can be justified, on the grounds that "saying X, without saying Y and Z" is indisputably fraud, under all circumstances (those this is a very high bar to clear, and I'm not sure that the prohibition clears it).