There is no global jurisdiction. So what? What global jurisdiction do you appeal to for your personal definition of “world champion”?
If you are admitting that one of the definitions applies, then what exactly are you disputing?
And who are you to decide that every use of the term by someone else must reflect the particular (literal) definition that appeals to you?
So what?
I wouldn’t care what you called yourself. I certainly would get into an international tizzy over it or label it a cultural defect on your part.
More importantly, it would be relevant whether you made this claim as a literal fact or because you were using this term as puffery to promote your goods or services. If the former, I could just figure out for myself what I thought the literal meaning of “best football player ever” was and decide that you were wrong, if I even cared to give it that much thought. If you were using it in the manner of commercial puffery, I’d have no motivation at all to even consider the literal meaning of the term and wish you luck in promoting your product.
And demanding this cite is supposed to prove what? There are millions of terms used in commerce in the world and the vast majority of them have not been subjected to judicial or academic scrutiny. That’s a fact of law, a fact of law, and a fact of language. You think you can send me on a wild goose chase to try to find some kind of authority when none is likely to exist?
Even if I were to come up with an actual court opinion specifically stating that the term “world champion” is mere commercial puffery or an academic study stating that this term is understood to have non-literal meanings among the consuming public, would you actually be so willing to change your position?
The mere fact that the concept of commercial puffery exists somewhere in the world plus the example of the use of the term by a variety of individuals and entities should be enough to satisfy you that this is the case.
In fact, if you are arguing with any sincerity at all, the mere fact that at least two persons — that is, you and I and other people in this thread — disagree over the implications of the term should be enough to satisfy you that there is no general understanding that this term as used in commerce is meant literally. Professional sports leagues and clubs and individuals have been making claims to being world’s champions going back at least to the 19th century. That’s evidence enough.