Children's Court president Denis Reynolds warned a year ago that oppressive regimes for WA youths with behaviour issues in detention could harm their mental health.
He said the treatment of one teenager was "psychological punishment" that was counterproductive, cruel and inhumane.
Judge Reynolds highlighted his concerns after the Department of Corrective Services applied to shift the 17½-year-old from Banksia Hill Detention Centre to an adult jail.
His problem behaviour included repeatedly assaulting officers and damaging property.
The judgment, made in March and obtained after last month's riot at Banksia, called for a review of internal regimes and conditions imposed on juveniles with behaviour and management issues.
Judge Reynolds said regimes imposed on the teenager were oppressive, arguably breached laws and the Convention on the Rights of the Child, amounted to "psychological subjugation" and could easily make serious mental health problems worse for young detainees.
A department spokesman said a review of "regression management" regimes was not completed but the way detainees' behaviour was managed had changed.
He said young people with behaviour issues who were managed through individual regimes were subject to a committee review.
The teenager was removed from the general detention population in October 2011 and put in a special-purpose unit after a serious assault on an officer in December 2011.
For a month, he was segregated from the centre's population and assigned education and reading in his cell. He was restrained when taken to the shower and any movements involved a leg chain.
In an affidavit, the teenager said he was lonely, stressed and did not know how much more he could take. He was given books but could "only read a little bit".
Judge Reynolds accepted the teen was a significant risk to staff but was not satisfied the youth could be better managed in an adult jail exposed to adult criminals.He said better staff training and support could help.
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