The New Zealand Law Society says the Fiji interim regime's latest decree goes against basic principles of the rule of law.
The Fiji National Provident Fund decree regulates changes to the country's main pension scheme, and does not allow anyone to challenge its provisions in court.
It also gives the Attorney-General the power to stop any challenge already underway.
The chairman of the society's Rule of Law Committee Austin Forbes QC says there are isolated and sometimes justifiable no-challenge provisions in other countries including New Zealand.
He says the catch-all nature of the Fiji decree is indefensible.
"That's a breach of the accepted principles of the rule of law that legislation does not take away existing rights which are in the form of a current court proceeding that's already been initiated. Secondly on a broader level I'm afraid it only demonstrates the continuing erosion of the rule of law and indeed democratic values in Fiji."
Mr Forbes says the decree further threatens the independence of judges in Fiji.