The inquiry was sparked by the ACT government's wrongful removal of five Aboriginal children from their mother in 2013. The case was settled in court early last year, ending the mother's five-year battle to have her children returned to her care.
Evidence to the inquiry has so far painted the picture of a system plagued by a lack of transparency, with a combination of legal and bureaucratic barriers, as well as a culture of secrecy in the ACT's child protection agency, blocking foster carers, family members and advocates from accessing critical information.
The majority of witnesses have expressed concern that so few decisions made by the child protection agency, including those regarding the child's living arrangements, are subject to external review under territory law.
At Tuesday's hearing, Dr Watchirs said the absence of that legal "safeguard" was among the reasons why the child protection legislation was not compatible with human rights law.
The ACT in 2004 became the first Australian jurisdiction to enact a human rights act. Bills introduced to the ACT Legislative Assembly include a statement on how that piece of legislation complies with human rights law.
"As a human rights jurisdiction, the starting point should be, naturally, the Human Rights Act," Dr Watchirs said.
"However, the underlying framework that is the Children and Young People Act falls well short of compatibility.
"Despite being a human rights jurisdiction for 16 years, very basic safeguards such as external review and accessibility to information, which are a matter of course in other jurisdictions, are simply unobtainable presently in the ACT.
"These deficiencies need to be addressed as a priority."
Conducting a review of which decisions should be subject to external scrutiny was among the recommendations from Laurie Glanfield's 2016 inquiry into the territory's child protection system.
The ACT government last year started the review, publishing a discussion paper that flagged a potential widening of the scope of child protection decisions that could be externally reviewed.
The government has hired a consultant to examine submissions to the discussion paper.
In her evidence to Tuesday's hearing, ACT Council of Social Service chief executive Emma Campbell described the absence of a "rigorous right of review" for child protection decisions in the ACT as "troubling".
All administrative decisions made by the director-general under a care plan or a care and protection order should be subject to external review, Dr Campbell said.
"That would include [decisions] on where [the child] lives, which family members or other people the child might have contact with, as well as frequency of contact," she said.
The ACT Civil and Administrative Tribunal was the most appropriate forum to have those decisions reviewed, she said.
Minister for Children, Youth and Families Rachel Stephen-Smith is scheduled to appear before the inquiry on Wednesday afternoon.