It was not always like this. Before 1994, persons suspected of unlawful immigration status could be arrested and detained by migration officials. However, they had to be brought before a magistrate within 72 hours and thereafter every 7 days until their status was determined. Incarceration had to be for a purpose relating either to determination of their status or their removal from the country. This is the regime that should be restored. If individuals pose a threat, they should be dealt with under the criminal justice system. This already allows for preventative detention, release on condition and intensive oversight through control orders and the like.
Mandatory immigration detention is a policy that has caused indiscriminate harm, including death, and permanent incapacity. It has been rightly described as our national shame.