Ms Douglas wrote a report for the Law Foundation two years ago which said the country's adult guardianship law, the Protection of Personal and Property Rights Act, was out of date - especially considering people were living for longer.
"There are many people who have impaired capacity for decision-making, with dementia for example, and are particularly vulnerable in the health system," she said.
"There is a need for a legal framework to better serve and promote their interests as well as the many challenges and inefficiencies of working within the current law."
New Zealanders can create an enduring power of attorney - a statement someone can act on their behalf if they become unable to do so - but there is no register for those orders or body overseeing their enforcement, meaning people's intentions might be overridden, she said.
"There are also liberty issues at stake, for example the basis upon which we admit people who do not have capacity or competence to consent to admission to a secure dementia unit."
