A narrative has formed in which the courts and crafty lawyers regularly stymie the efforts of the federal government and police to rid the streets of thugs.

Three such cases have recently come to light. One involves a 25-year-old South Sudanese armed robber who came to Australia on a refugee visa - he had his deportation order put on hold by a Federal Court judge because his siblings might be negatively affected.

An apparent Apex gang leader, Isaac Gatkuoth, served 16 months in jail for a violent carjacking while high on ice and is now fighting his deportation order. In another example, a South Sudanese criminal was granted a reprieve because he wasn't given adequate notice of his visa cancellation.

Such instances compel particular angst on talkback radio and in other forums that lend themselves to consternation about law and order. At times, cabinet ministers have joined in the criticism of weak judges and pesky appeals tribunals.

The reality is somewhat different. Judges are not overturning decisions to deport criminals - in fact, they do not even have that power. They are simply examining whether the minister has followed proper legal process in making his decision.

Here's an example. Someone who is not an Australian citizen commits his third crime and the minister - or a departmental delegate - decides to cancel his visa and deport him. If the minister makes the decision personally, there is no right of review at the Administrative Appeals Tribunal. If it was a delegate, the man can try his luck at the AAT.

In either case, the man can go to the Federal Court for judicial review. This is not an appeal. The judge cannot reinstate his visa, but she can find that the law wasn't properly followed - such as a failure to even consider the impact of deportation upon the man's family.

"What the court does is it looks at the legality of the decision that has been made," explains Mary Crock, professor of law at Sydney University. "It's [then] open to the government or the tribunal to go back and effectively make the same decision but in a legally correct way, taking into account all relevant considerations."

In other words, it doesn't change anything. The minister will almost always make the same decision again, but in a more legally robust way.

"All the minister has to do is make the decision correctly and the person gets deported," says Nicholas Poynder, a Sydney-based barrister specialising in immigration. "If the decision is legally erroneous then the court is entitled to set that aside and return it to the decision-maker to do properly."

Mr Poynder argues the government actually has "extraordinary power" in immigration cases. For one thing, the minister (at this time Peter Dutton) has the power to set aside a decision of the AAT and substitute a new one - basically, he can overrule the reviewing authority. This happened to one of Mr Poynder's clients two days before Christmas. "I find that unfair," he says.

Neither does Mr Poynder believe the AAT is a soft touch, hellbent on reversing the government's decisions. He says it is like any tribunal - some members will be more sympathetic than others, and will approach a particular set of facts from different perspectives. In all these cases, the minister is represented at the tribunal hearing anyway.

Critically, it is also the case that most of these people are behind bars while their legal appeals are underway - they are not out on the streets. If someone's visa is cancelled while they are in jail, they go straight into immigration detention at the conclusion of their prison term. If they are not required to attend a Federal Court hearing in Sydney or Melbourne, they may be held at Christmas Island or in Western Australia.

"They're not a threat to the Australian community at that time," says Carina Ford, who runs a large migration law agency based in Footscray. "These people have completed their sentences, [but] they're still in detention."

Ms Ford, who regularly works on cases involving Sudanese and African migrants, says a black-and-white view of these matters is too simplistic. She believes decision-makers should take into account the impact of deportation on families, as well as the risks of returning a person to the country from which they fled, and whether they were given enough support in the first place.

"When you're dealing with it at the coalface, you can see the personal impact on families," she says. "This concept where you can simply send them back and get rid of them is just not accurate."