Earlier quoted context omitted.
“Nothing much seems to be working” because the government is completely unserious about stopping the boats and is unwilling to do any of the things that might actually work. They could stop them in a week if they actually wanted to.
Legally and morally? What is your solution?
Australia did exactly this (in the face of howling opposition) and it worked: illegal boat arrivals dropped from ~20,000 per year to almost zero. Thousands of people used to drown attempting the crossing, now no-one drowns. There's your moral case.
Legally, Parliament is sovereign. If the current legal framework doesn't allow it, change the law. Except they won't, because they don't want to solve the problem and they use the law as an excuse as if they aren't the fucking government.