I think what we're saying is that the conflict between the state and federal government is a problem to be hashed out between the state and federal government and not the problem of the guy who received an invitation from the state government.
(Djokovic didn't just fly in without any piece of paper; he learned too late that the piece of paper he had in his hand was inadequate. And the question still stands: Did he have any reason to suspect that he didn't have the right paperwork, or did he act in good faith?)
Well, now I am going to exaggerate about your point, but as an example, if California invited a known terrorist from Iran to visit and give a speech in San Francisco(very possible with California’s state government!), would that supersede the USA Federal Government from rejecting a visa and keep that person from entering the USA? All the non-Aussie citizens tennis players and supporting staff have to have a sports working visa to get into Australia for the Open. Covid questions and restrictions have been added to that type of visa. Of course, like some countries, the main reason for the working visa is for Australia to collect taxes. It looks like 99% of the foreign players and staff have filled out the visa forms properly to come to the Open. By the way, I am totally against these stupid Covid restrictions on traveling in and out of Australia and between our states. But what we can see here, from what is going on in the USA, the vaccine mandates and rules are much worse in your leftist controlled states like California, New York, New Jersey, Illinois, etc. Let’s face it, if the Supreme Court doesn’t reject Biden’s mandates, you will will have in place Federal vaccine mandates, something we do not have here in Oz. And, unlike poor naturalman, who lives in the worst leftist state in Oz, I live where we have have had very little restrictions and travel restrictions, compared to most of the USA.