ICANN has no sovereign position to censor. In fact, I think ICANN does not wish to have any role in "ordaining any content."

ICANN's only function is to administrate the use and registration of TLDs.

Under what sovereign's law would *obscene* be assessed?

Under sharia law? A woman not in a burka under that law is *obscene*.

As far as child pornography is concerned ? if ICANN decides to cancel that domain's registration with some due process to the accused violator ? I would have no issue with this.
But, only on this narrow issue and not in general censorship.