The Northern Territory police union says the emergency declaration and youth curfew imposed on the town of Alice Springs could be unlawful.
The two-week youth curfew was imposed on March 27 when Chief Minister Eva Lawler declared an emergency following escalating violence in the red centre.
Ms Lawler said the emergency powers granted to her by the Emergency Management Act 2013 allowed her to impose the 6pm children's curfew.
But police association president Nathan Finn said the union had received legal advice that the emergency declaration could have been illegal.
"I don't know what event has or hasn't occurred, but presume from the Chief Minister's media interviews that the relevant event is the recent civil unrest in the Alice Springs precinct, and (a) potential event is likely further civil unrest in the Alice Springs precinct," he said in a statement on Tuesday.
"Should that be the case, section 4.2 of the Act specifically precludes a person (i.e. the Minister or police operating under his declaration) using the Act to 'put down a civil disturbance'."
Mr Finn said police were at legal risk by being required to exercise powers which could be unlawful.
"It is critical the declaration from Police Minister Brent Potter is lawful, and ensures our members are protected to undertake the roles they have been directed to do," he said.
Mr Finn said he spoke to Police Commissioner Michael Murphy about his concerns but Mr Murphy told ABC Breakfast he was not worried about the potential of a legal challenge by the association.
"Usually, the act is implemented for emergency management hazards, cyclones, floods and fires," he said.
He said he was not using the act for the suppression of civil disorder, armed combat, or ending a strike - all of which would not be permitted.
"The act talks about an event which leads to the loss or damage of property, loss of life or distress of people," he said.
Ms Lawler said the Mr Finn should visit Alice Springs and talk to community members before passing judgment on government policy.
"I can assure Mr Finn and whoever else that we've got amazing lawyers that will obviously go into bat for the NT government's decision," she said.
"So it's a total waste of their resources."
The 14-day curfew was imposed after chaos hit the town last week when youths attacked the Todd Tavern as tensions escalated following the death of a teenager.
Brawls continued later in the evening as family members mourned the death, with up to 150 people clashing in town camps.
Rising tensions in the desert town were inflamed by the death of an 18-year-old in a fatal car accident in early March.
He died after hanging out of the window of a stolen car that rolled over in the Alice Springs CBD and was left there by the driver and passengers.
The attack on the Todd Tavern caused about $30,000 damage.
After the emergency declaration was made on the same day, police deployed an extra 58 police officers to the town.
More than 50 young people were found violating the curfew on Sunday night, but Ms Lawler said data on whether the measures are working to bring down crime is not yet available.
