Novak Djokovic’s arrival in Australia on Wednesday was mired in confusion after an airport dispute about the validity of his visa and questions about the evidence supporting the medical exemption he received to play in this month’s Australian Open.

One day after Djokovic, a 20-time Grand Slam champion and an outspoken critic of vaccine mandates, announced that he had received a medical exemption that would allow him to defend his Australian Open title in Melbourne, he found himself in limbo unable to enter the country. Tournament rules require that participants be vaccinated against the coronavirus or receive a medical exemption.

Tournament officials confirmed in a statement on Tuesday that Djokovic, the world’s No. 1-ranked men’s tennis player, had received a medical exemption after a review of his application by two independent panels, a procedure that strongly suggests he remains unvaccinated. But his entry into the country, several top Australian officials quickly noted, was still a question for the federal government.

An Australian newspaper, The Age, reported that a plane carrying Djokovic landed at Melbourne’s Tullamarine Airport about 11:30 p.m. local time on Wednesday, but that Djokovic was still being questioned by officials from the Australian Border Force more than six hours later. The problem, according to multiple news media reports in Australia, was related to the type of visa Djokovic applied for to enter the country.

Australia’s prime minister, Scott Morrison, invoked the government’s authority to deny entry to Djokovic.

“Any individual seeking to enter Australia must comply with our border requirements,” Morrison said.

“We await his presentation and what evidence he provides us to support that,” Morrison added. “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. There should be no special rules for Novak Djokovic at all. None whatsoever.”

Border officials appeared to have appealed to officials of the Australian state of Victoria, which contains Melbourne, where the Open is held, in an effort to resolve the matter. But the request was rejected, according to Victoria’s acting sports minister, Jaala Pulford, who wrote on Twitter that “visa approvals are a matter for the federal government.”

A spokeswoman for the Border Force said it had reached out to the Victorian government asking for more information about the documentation supporting Djokovic’s medical exemption and “to validate their public statements about their support for his entry,” but the spokeswoman denied that the force had requested Victorian government support for his visa, The Age reported.

Pulford did not immediately respond to requests for comment. Australia’s home affairs department, which oversees the country’s Border Force; Melbourne Airport; and Tennis Australia, the sport’s governing body in the country and the organizer of the Australian Open, also did not immediately respond to requests for comment.

The decision to grant Djokovic a medical exemption was greeted with skepticism and resignation from some of his fellow players; outrage from Australians; and thinly veiled warnings from government officials that he was not exempt from the strict application of the country’s border rules.

Earlier Wednesday, Australia’s minister for home affairs, Kim Andrews, released a statement that noted the government had the authority to block Djokovic from entering the country. In a statement headlined “Australia’s Border Rules Apply to Everyone,” Andrews said that “while the Victorian Government and Tennis Australia may permit a non-vaccinated player to compete in the Australian Open, it is the Commonwealth Government that will enforce our requirements at the Australian border.”

Djokovic, if allowed to play, would be pursuing a record 10th men’s singles title at the Australian Open. He is tied with Rafael Nadal and Roger Federer for the most Grand Slam men’s singles titles with 20.

Djokovic has long expressed some non-traditional views of science and medicine (he once asserted that prayer and belief could purify toxic water) and has had a complicated relationship with the pandemic.

In June 2020, when sports were still largely shut down, and long before experts deemed it safe for people to gather and large events to take place, Djokovic organized a series of exhibition matches in Serbia and Croatia and invited several of the world’s top players to participate. They obliged, and several of them became infected with the coronavirus, including Djokovic.

Matthew Futterman contributed reporting.