OPINION: Whatever the election outcome, we can expect that asylum seekers will argue their case in the High Court. This has already begun with an attack on Labor's Papua New Guinea plan. A constitutional challenge to Coalition policy would also seem certain.

A big problem facing an Abbott government would be how to deal with the 30,000 asylum seekers already in Australia who have arrived by boat. The Coalition would expand the facilities on Manus Island and Nauru but this would not be sufficient to accommodate them.

Processing these people in Australia under the present law would also take years. This is due in part to the fact that a decision to deny someone asylum can be reviewed by the Refugee Review Tribunal and, if the tribunal finds against them, its decision can be challenged in court.

The Coalition proposes to speed up the processing of asylum seekers by deciding more quickly whether they are refugees and by denying them any right of appeal. The present system would be replaced by one in which all decisions are made by officers or subcontractors of the Immigration Department.

This plan is problematic on two grounds.

First, making all determinations within the Immigration Department is not likely to lead to accurate decision making. Its officials tend to be under severe time pressure, and have been prone to a high rate of error.

This is reflected in the fact that 70 to 80 per cent of their recent decisions to deny asylum have been overturned when reviewed by an external, independent tribunal or court. The cost of inaccurate decision making here is very significant. Wrongly returning people to their country of origin will leave them open to persecution, and in some cases could lead to their death.

Second, the plan may be struck down as unconstitutional. The jurisdiction of the High Court to review decisions by all officers of the Commonwealth is guaranteed by section 75(v) of the constitution.

Attempts to bypass this have failed. In 2001, the Howard government had the Migration Act changed to state that decisions of the Refugee Review Tribunal were "final and conclusive" and "must not be challenged, appealed against, reviewed, quashed or called in question in any court".

An asylum seeker who had failed in the tribunal sought a review in the High Court on the basis that he had been denied natural justice. The government countered by saying this was prohibited by the act.

It was held in 2003 in a case called Plaintiff S157, in which I appeared for the asylum seeker, that the Migration Act could not stop review by the High Court. The court found that a law is invalid if "it attempted to oust the jurisdiction conferred on the High Court by s 75(v) of the constitution".

In doing so, the High Court invoked the rule of law. It recognised that no government officials could be allowed to operate outside the law, and that this must be protected against by the High Court having jurisdiction to rule on their actions.

Opposition immigration spokesman Scott Morrison has conceded that his approach is legally difficult. It is more than that. It represents an attempt to revive a Howard government policy that was overturned by the High Court. There is no reason to think that the court would decide the matter differently a decade later.

The Coalition has other options. It could retain the jurisdiction of the High Court, while abolishing the appeal rights of asylum seekers to the tribunal and other federal courts. This would be sound constitutionally and would streamline the process.

However, it would be unworkable. It would leave the seven judges of the High Court as the sole avenue for external review of the claims of more than 30,000 asylum seekers. The court would assume an unmanageable workload that would compromise its other functions. It would also become a new bottleneck in the process.

There is merit in reducing the often overlong time taken to resolve whether a person is a refugee. Cutting this back will save public money and limit the period that a person spends in detention. However, achieving this has proved inordinately difficult.

The Coalition plan is not legally feasible. It would either be struck down as unconstitutional or, if the High Court were left as the sole avenue of appeal, introduce a new set of problems. Either way, the Coalition would find itself back at square one.

George Williams is a Professor of Law at UNSW. 

This opinion piece was first published in The Sydney Morning Herald.