Canberra is in a state of emergency over the coronavirus pandemic as the national capital records its second case.
ACT Health Minister Rachel Stephen-Smith said the declaration had been signed off on Monday afternoon.
The declaration initially lasts for five days and then can be renewed.
It comes after Canberra health authorities confirmed the city's second case of coronavirus, with another man in his 30s testing positive on Sunday.
The capital's chief medical officer Dr Kerryn Coleman said a few close contacts of the man were tested and are under isolation.
Authorities believe the man contracted the virus in NSW and he is now in self-isolation at home.
Dr Coleman said the man was infectious on Saturday and had been at the Art Not Apart festival from 4pm to 5pm on Saturday before going to Capital Brewing from 5pm to 6.30pm.
"We believe the potential exposure to any members of public or staff at these events is very low," she told reporters in Canberra.
"Be aware of the symptoms and just let us know if you come down with any of these symptoms."
Capital Brewing says it beefed up its cleaning procedures on Saturday morning, including regularly sanitising shared surfaces.
The venue remains open and has been assured by ACT Health it's safe to visit.
Dr Coleman said the man was a member of a local school community, but not a staff member, with education authorities being provided advice.
Ms Stephen-Smith said the emergency declaration would give the ACT's chief health officer more powers to enforce isolation and quarantines.
Canberrans could face fines of up to $9000 for not obeying containment measures.
Chief Minister Andrew Barr flagged potential changes to the territory's upcoming October election, with the government receiving medical advice on how to proceed.
"Clearly there would be some things that people would be used to as far as Australian elections that would not be a feature," Mr Barr told reporters at Monday's press conference.
"This is not business as usual ... but that doesn't mean democracy is suspended."
Moves to close local courts would be a matter for the justice system, he said.
Closing national cultural institutions or cancelling ANZAC Day services in Canberra would be a decision for federal government.