Djokovic's lawyers have moved onto their arguments for why the border official made the wrong decision.

Their chief contention is that the official wasn't properly aware of national guidelines which state that a Covid infection is a medical exemption.

Those guidelines are from the Australian Technical Advisory Group on Immunisation (ATAGI) and which the federal government refers to for definitions on what counts as a medical exemption.

The lawyers point out how when a visitor is entering Australia and making their travel declaration form, that online form points to ATAGI as the source of definition for a covid medical exemption.

They're saying - why didn't the border official know this rule? And there's no evidence that the border official attempted to check the ATAGI guidelines.

Katie Silver
BBC News, Melbourne

The Grmusa children are third generation Serbian-Australians.

Mihajlo, 11, Milan 16, and Tamara, 15, describe themselves as big Novak fans and say he’s an ambassador of Serbia who represents their culture.

“We’re just here to support him - it’s not fair what’s happened to him,” said Milan outside the court.

Tamara said: “We want him to be allowed out to play and win the Australian Open once again.”

Simon Atkinson
BBC News, Melbourne

It looks like Novak Djokovic has been allowed out of his detention hotel to watch the proceedings elsewhere in Melbourne.

An order that was made yesterday – but just released by the court – instructs the government to “take all steps and do all things as may be necessary” to bring Djokovic to a “premises” specified by his solicitors.

But for fans hoping this means he’s going to a new hotel with a tennis court, well that looks unlikely.

Djokovic will be returned to detention at the conclusion of each hearing.

We’re waiting to see if his legal team can give us more details where he is. But it almost certainly won’t be the offices of the law firm who have a no vaccination, no entry policy, external.

Russell Fuller
Tennis correspondent in Melbourne

Image source, Reuters

Novak Djokovic is not pictured on the feed from the Federal Court, but you assume he is following proceedings from his asylum hotel.

There is no point him worrying about the Australian Open until he has won this court battle, but there is no doubt his opponents have stolen a march on him over the past week.

Rafa Nadal won the ATP title in Melbourne yesterday, and Daniil Medvedev and Alex Zverev both got some wins under their belt while competing for Russia and Germany in the ATP Cup.

All three are resting and practising this week. In comparison to Djokovic, they have hardly a care in the world.

But we'll bring you more updates as soon as we can. The court has said it is trying to fix technical problems.

Judge Kelly has described again the conditions Novak Djokovic faced when he arrived near midnight in Australia.

The tennis star was told after hours of waiting at 4am that officers intended to cancel his visa.

He didn't understand why as he thought he had given all evidence of his exemption to officers. And, as we've reported - immigration officials failed to tell Djokovic why his visa was being cancelled so the tennis star didn't know what was wrong with his visa.

Djokovic then requested more time, until 8.30am, so he could get advice from his lawyers and Tennis Australia. But he was pressured by officials to submit to the visa cancellation earlier.

The judge appears in tone very unimpressed by these facts. Kelly notes how the player was basically "incommunicado", in other words without access to any help.

Djokovic's lawyers argue that the conditions are unacceptable, and that he was being treated unfairly. How Djokovic was treated at the airport also goes towards his team's other arguments of unreasonable treatment and unfair procedure. They're yet to raise those legal grounds.

Katie Silver
BBC News, Melbourne

Image source, Police and protesters outside the Park Hotel earlier today

There were some protests early today outside the Park Hotel, where it is believed Djokovic is staying.

Police and refugee activists were engaged in a heated discussion near the entrance to the hotel before the protesters walked off, with one woman yelling behind her.

Overnight, protesters erected a banner on the hotel’s roof calling for more action to free detained refugees.

Our colleague Alice Cuddy has written a piece here on why the hotel has drawn controversy for its treatment of migrants.

Anti-vaxxers and Serbian supporters have also been protesting outside the hotel in the past few days.

Judge Anthony Kelly is agreeing with Djokovic's lawyer's argument that the tennis player presented all the necessary medical evidence to officials.

He says he's quite "agitated" by what he's heard so far - and repeats the fact that Djokovic's exemption was granted by two separate medical boards in Australia.

"What more could this man have done?" says the judge.

Djokovic entered Australia on the understanding his exemption due to a Covid infection was valid, his lawyer says.

Lawyer Nick Wood says it was granted to the player by two separate medical boards.

"He had done absolutely everything. He had engaged with everything that was required of him by Tennis Australia," says Mr Wood.

"Djokovic was not even identified, as he should be [as to where he went wrong]."

The tennis player's barrister is now running through the legal processes required under the Migration Act for officers to cancel someone's visa.

This includes giving proper notice to Djokovic and adequate time for his right of reply, as well as telling him the grounds for why his visa is being cancelled.

His lawyers point out that the notice given to Djokovic did not refer to the right section of the law - that is, the grounds by which his visa would be cancelled.

Djokovic's barrister, Nick Wood, has been discussing what was required of Djokovic prior to entering Australia.

He says the tennis player made a full travel declaration including evidence of his medical exemption due to his Covid infection.

He says that none of the Australian laws explicitly state that people cannot enter Australia unless they are vaccinated or that they need to provide such proof.

Judge Anthony Kelly agrees, saying that laws are written to require necessary evidence.

“Reflecting on this problem that has arisen in this case is that the well-worn idea that if the parliament wanted something to be a requirement it would have said so," he says.

Ok, we've gained access to the hearing at last.

Djokovic's lawyers are arguing the first four of their seven legal grounds. They are arguing that border officials failed to give valid notice of the government's intention to cancel Djokovic's visa.

Before cancelling someone's visa, the Migration Act requires officials to give proper notice and time for people to respond.

Djokovic's lawyers are attempting to argue that officials didn't follow this process properly.

Frances Mao
BBC News

Image source, Reuters

Central to the case today will be the processes immigration officials used to cancel Djokovic's visa - and whether these were followed properly.

The Australian Border Force (ABF) was able to cancel Djokovic's visa at the airport under powers given to them in the nation's laws.

Specifically the power under s116 (e)(i) of the Migration Act., external

It allows the government to cancel someone's visa if they present a risk to "the health, safety or good order of the Australian community..."

The ABF decided that Djokovic, being unvaccinated, posed such a threat.

However, the tennis star's lawyers argue that he presented "miniscule" risk, given he had already had Covid, reducing his risk of contracting it again and passing it on to others.

Australia is already in the grip of an Omicron wave and seeing over 90,000 cases a day. Djokovic's entry hardly makes any difference, his lawyers said in their court documents.

The court has confirmed the hearing is now under way.

But due to the technical difficulties at the court, it is still not possible to hear what's going on.

"The court is working to rectify the situation," a representative said.

Djokovic's lawyers will start first. According to their weekend court submissions, they will argue that the tennis player was treated unfairly and without proper process at the airport.

They will also argue that Australian government advice includes a recent Covid infection as a valid exemption to the vaccine requirement for entry.

Simon Atkinson
BBC News, Melbourne

While the court looks into its technical issues, let's look at what might happen.

There's no certainty we'll get a decision from Judge Anthony Kelly today. It could well be reserved until Tuesday.

But if Novak Djokovic does win his appeal there’s no guarantee he'll get to play in the Australian Open.

The immigration minister still has the right to cancel the visa again - though if that happened it could be an even worse look for the country than this fiasco has already become.

The Federal Circuit Court has advised there are technical delays.

"It is being worked on," a court spokesman says.

There has always been a feeling that Djokovic wants the same adoration that fellow champions Roger Federer and Rafael Nadal have received from the crowds throughout their career.

He is a more volatile figure than both Federer and Nadal, as he showed at the 2020 US Open when he was defaulted for hitting a lineswoman in the throat with a ball.

His over the top celebrations – where he gestures to all four corners of the court – also grates on some.

Djokovic has in the past been accused by other players of exaggerating injuries and he was heavily criticised, notably by Australia’s Nick Kyrgios, for organising a tournament in June 2020 in the midst of Covid-19 pandemic.

A number of players subsequently tested positive for the virus and Djokovic later apologised.

Katie Silver
BBC News, Melbourne

This is the court where Djokovic’s team will have his case heard, beginning in about 15 minutes.

But they - and the world number one - won’t be in attendance, due to Covid restrictions.

Only the judge is expected to be in the room while others will appear by video link.

The judge has said if Novak Djokovic speaks it could speed up the progress of his case.

Image source, PA WIRE

There's been much controversy over Djokovic's bid to play in the Australian Open ever since he announced on 4 January that he had received a medical exemption to participate.

Australia requires all foreign visitors to be double vaccinated, or to complete 14 days in quarantine.

Many ordinary Aussies were up in arms that a tennis superstar was apparently being allowed straight into the country.

The political fallout led to PM Scott Morrison warning Djokovic that he would be sent home if he failed to provide proper medical proof for his exemption - despite initially saying he’d allow the state of Victoria to decide.

Djokovic landed at Melbourne Airport near midnight on Wednesday and was promptly assessed and rejected for entry.

After spending eight hours at the airport his visa was cancelled and he was taken into temporary immigration detention.

His lawyers say he met the criteria for a vaccine exemption certificate because of a Covid infection on 16 December - and that he had the backing of state and sporting bodies.

But Australia's federal government dismissed the prior infection as a valid reason for an exemption.

It's been a chaotic row on many levels, played out under the glare of global publicity. It's now up to the court to decide.

Read more: The twists and turns of his Djokovic’s Australia mess

It's due to be a one-day hearing where both sides will present their submissions.

Djokovic’s lawyers will start first, at 10:00 local (that’s 23:00 GMT on Sunday).

The Australian government’s representatives will then respond in the afternoon at 15:00 (04:00 GMT Monday).

The judge has ordered that both sides should have no longer than 120 minutes for oral submissions. So in theory all arguments should be heard by 17:00.