Melbourne, Australia — This city is in the middle of the country. It was Novak Djokovic’s lawyer’s job to say that the tennis star had been diagnosed with the coronavirus in December. The Australian government had been wrong to cancel his visa this week because it required him to get a vaccine for the virus, they said in a court filing on Saturday.

His goal is to defend his men’s singles title at the Australian Open this month. When he arrived at Melbourne airport on Thursday, he was turned away. They say they canceled his visa because he didn’t show that he could be exempt from Australia’s requirement that newcomers be vaccinated against the coronavirus.

Because of a positive coronavirus test on December 16, Novak Djokovic’s lawyers said that Tennis Australia gave him an exemption from vaccines because, 14 days later, he hadn’t been sick for 72 hours.

A group of lawyers said that the conditions of the exemption were in line with the recommendations of Australia’s immunization advisory body. As a result of these and other things, “Novak Djokovic’s knew that he could enter Australia,” the filing said.

When Mr. Djokovic, who doesn’t believe that vaccines work, goes to court on Monday, he’ll be in quarantine at a hotel in Melbourne. He’s appealing the government’s decision to cut off his visa.

In June 2020, he told the public that he and his wife had both been infected with the coronavirus. His December infection had not been made public before then.

Australia’s immunization advisory body had said that a coronavirus infection in the last six months should not make him have to get vaccinated. Djokovic’s lawyers say that the Australian government “radically and fundamentally” misunderstood or misapplied this advice.

The filing also says that Djokovic was not treated fairly when he arrived in Australia. The filing says he was held at the airport by immigration officials from about midnight to 8 a.m., the filing says.

Djokovic’s lawyers say immigration officials told him that a decision about his visa would not be made until after 8.30 a.m., when he had a chance to talk to Tennis Australia officials. They say that was not the case. But around 6 a.m., they say, he was pushed to make a quick decision. He agreed, “thinking he had no choice,” and was told at 7:42 a.m. that his visa had been canceled, the filing says.