The prime minister of Australia is warning that tennis star Novak Djokovic must prove he has a valid medical reason to be exempt from COVID-19 vaccine requirements or he won’t be allowed to enter the country for the Australian Open. 

Djokovic, who has said he is “opposed to vaccination,” this week announced he would compete in the Australian Open after receiving a medical exemption from the requirement that players be vaccinated against COVID-19. But Australian Prime Minister Scott Morrison is now warning that he will need to provide valid proof backing up the need for his exemption, The Washington Post reports. 

“If he’s not vaccinated, he must provide acceptable proof that he cannot be vaccinated for medical reasons to be able to access the same travel arrangements as fully vaccinated travelers,” Morrison said. “So we await his presentation and what evidence he provides to support that. 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.” 

Australian Open organizers said that Djokovic received his exemption “following a rigorous review process involving two separate independent panels of medical experts.” By Thursday, though, the Australian newspaper The Age reported Djokovic’s entry “was in limbo” as he faced questions at the airport in Melbourne as to whether he had “adequate documentation to prove the reason for his exemption.” The report added, “It was not clear whether a COVID-19 infection in the past six months — which is suspected to be the justification for the player’s exemption — was sufficient to secure entry into Australia under federal guidelines.” Additionally, the Times of London reported a member of Djokovic’s team mistakenly requested a type of visa “that does not apply to those who have received medical exemptions from a COVID-19 vaccine.” 

Morrison previously said there “should be no special rules for Novak Djokovic at all — none whatsoever.”