It's important to clarify. He was promised entry by the government then only had his visa cancelled on arrival after the political climate changed.
Clarification: It was Tennis Australia who told him he could play, not the Australian government.
Then, based on that, the Australian embassy delivered a visa for his entry on Australian territory. That visa was then rescinded by a deputy assistant directly under the Minister of Foreign affairs after his plane from Dubai took off.
So "the government" all the way, no Tennis Australia in sight.
They have litterally made the rules, and are sometimes delegated to adjudicate on specific cases.
Checking that would have taken you exactly 5 seconds. It's litterally on their web page header, but in their statutes as well.
https://abcnews.go.com/International/djokovic-courts-controv...
Either that, or don't organize event at all if you have some concerns. Leaving to individual athletes to navigate country's ever changing visa rules is not fair or realistic. Even lawyers on Australian law subredit couldn't tell for sure how judge will rule in Djokovic's case and which laws and statutes should be taken into account and which have precedence.
This is not only about Djokovic. It's also about tennis players who received Sputnik vaccine and couldn't go to Australia Open. Yet we have numbers from few non-Russia countries which tell us it's in the similarly effective as other vaccines.
Also, I'm not talking about tennis and Australia only, too many times athletes were stopped from competing because of politics and it never seems fair.