It's a violation of their bodily integrity
Recently passed laws have given the centres new powers to control detainees, including using attack dogs.
Young detainees can also be given medical procedures without permission and can be isolated indefinitely.
The NSW Government pushed through the changes after a riot earlier in the year at the Acmena centre at Grafton on the state's north coast.
As of this week, if there is a riot or a disturbance at a juvenile centre, the Department of Corrective Services - the authority in charge of adult prisons - is allowed to step in and take charge.
Public Interest Advocacy Centre spokeswoman Anne Mainsbridge thinks some of these changes go against the Convention on the Rights of the Child as well as some international conventions.
"We're concerned that rights are going to be breached within detention and that that may lead to legal action through the courts for compensation or complaints to Australian and overseas human rights bodies," she said.
She is also particularly concerned that medical procedures will now be able to be forced on inmates without permission, which could include giving them drugs like sedatives.
"Now we say that's a significant trespass on their rights - it's a violation of their bodily integrity," she said.
"Really if a young person has the capacity to make a decision about medical treatment, then they shouldn't be treated without their consent simply because they're in a juvenile detention centre."
Legal Aid youth section worker Teresa O'Sullivan says some of her clients are at the Kariong youth detention centre, which was moved last year from the control of Juvenile Justice to the Department of Corrective Services.
She says one of her clients was segregated for three-and-a-half weeks.
"What really upset him was that he felt that he was being treated in a way that made him feel inhuman, and he was a really intelligent young man and he was saying, 'How is this going to make me a better person? It's just making me angrier and angrier'," she said.
"The problem for him was that he just had nothing to do. He didn't even have a pen and a piece of paper."
Michael Turtle for The World Yesterday