A majority of High Court justices have agreed that sections of the Migration Act, which had been interpreted to authorise indefinite detention, were "beyond legislative power." Why? Because indefinite detention breaches the separation of powers between executive government and the judiciary "because it is punitive". Sounds good, right?
But the person in question is not a nice person - he was convicted of the rape of a 10 year old girl. The trouble is, he happens to be a stateless person who cannot be deported to another country. Devilish dilemma.