Tennis player Novak Djokovic was denied entry to Australia on Thursday after almost nine hours stuck at an airport in Melbourne.
Australian Health Minister Greg Hunt said: "It's tough, but it's fair."
News agency Reuters said the tennis player would seek a federal injunction against the decision. An Australian court later said an injunction hearing would take place in the afternoon local time.
Why was Djokovic denied entry?
Prime Minister Scott Morrison told a press briefing Thursday that Djokovic failed to provide sufficient proof at the airport that would have allowed him to receive a medical exemption to enter Australia without being vaccinated against COVID-19.
Morrison added that Djokovic was not being "singled out."
"All I can say is that the evidence for medical exemption that was provided was found to be insufficient," Morrison said.
The Australian Open is scheduled to run from January 17 to January 30. The organizers have stipulated that only fully vaccinated players or those with an official medical exemption will be allowed to play.
Australia has strict COVID-related entry rules, stipulating that those wishing to visit the country must be fully vaccinated against the virus.
According to Tennis Australia chief Craig Tiley, there were exceptional circumstances, allowing certain individuals to enter the country, such as people who have recovered from the virus in the last six months or those that have an acute medical condition, thus unable to receive a vaccine.
Morrison said earlier Wednesday that Djokovic would need to "provide acceptable proof" that he cannot be vaccinated for medical reasons.
"If that evidence is insufficient, then he won't be treated any different to anyone else, and he'll be on the next plane home," Morrison said.
Tiley said 26 people had applied for an exemption and only a few were successful.
Vaccine skepticism
On Tuesday, Djokovic, an outspoken vaccine skeptic, claimed he fell into one of those categories, saying he had "exemption permission" and therefore would be able to compete.
There was a severe backlash in Australia to the decision to allow Djokovic an exemption, with many across the country, and in Melbourne in particular, enduring some of the world's strictest lockdown measures over the last two years of the pandemic.
With the entry denial, Djokovic chances of defending his title are now in jeopardy.
The 20-times major winner received some support late on Wednesday from Serbian President Aleksander Vucic.
"Serbia is doing everything to see that the harassment of Novak Djokovic is brought to an end immediately," Vucic said.
Morrison says 'rules are rules'
After the decision was announced on Thursday, Prime Minister Morrison said on Twitter that "rules are rules, especially when it comes to our borders."
"There should be no special rules for Novak Djokovic at all. None whatsoever," Morrison had told a news conference earlier on Wednesday.
