Like I said, if he is deem an imminent threat to society, charge him and take him to court. If found guilty by law, sentence etc. etc.
Otherwise, you will have to presume he is innocent.. keep watch or whatever, but you cannot bar him from his right to free speech, or stop him from being in public. To demand that because he could snap and do god knows what... trust me, you don't want to live in a society where people can be lock up "just in case".
Yes and free board and lodgings thanks to the Australian tax payer.....You can bet your a$se he does not have a job......Who would dare employe him?
Nothing to do but to think and plot his next move and yes, he cannot be arrested until he again commits some stupid crime....His brain will be working overtime after last Monday.