A murderer who shot dead a man outside a primary school will remain in jail after South Australia's parliament passed urgent laws closing a loophole that could have resulted in his release.

Convicted murderer Shane Andrews last week argued in the SA Supreme Court he was entitled to automatic parole because he was sentenced before Truth in Sentencing laws were introduced in 1994.

The court has yet to deliver its judgment.

But the legislation amending the Truth in Sentencing laws ensures that any prisoner with a non-parole period now must go before the state's parole board to seek release.

The board has three times previously refused Andrews' request for parole on the grounds he has expressed no contrition for his crime.

Andrews was convicted in 1991 of murdering Brian Lyden, and sentenced to life in prison with a non-parole period of 23 years.

The legislation passed by the SA parliament last night amending the Truth in Sentencing laws makes them applicable to all prisoners regardless of when they were sentenced.

"Regardless of what the Supreme Court now decides ... this unrepentant killer will not be released," SA Attorney-General Michael Atkinson said today in a statement.

"I have been advised that Andrews' court action has a slim chance of success. However, the government would be negligent if it didn't take every step to protect the public."