Any person returning from overseas will have to self-isolate at home or at a hotel accommodation and will risk fines of up to $20,000 if they breach the order.
“It’d be very unwise … to be subject to this quarantine and not do the right thing,” Premier Daniel Andrews told reporters on Monday.
“Not only are you putting the health of your loved ones and every family across Victoria at risk, but you’re also breaking the law.”
“I think common sense, and that sense that we’re all on this together will drive people to do the right thing.”
Victoria’s coronavirus tally is now 71 after 14 new cases were confirmed overnight.
The premier said the new measures are not designed to have zero new cases.
“Nothing we do can deliver this outcome. This is about flattening the curve,” Andrews said.
The self-isolation of all travellers coming into Australia was declared by Prime Minister Scott Morrison on Sunday.
Morrison said while a state of emergency was declared, it did not mean it was a “state of panic.”
From midday on Monday, for at least four weeks, authorised officers in Victoria can detain people, restrict movement and prevent entry to premises to protect the public.
Non-essential mass gatherings of more than 500 people such as cultural and sporting events and conferences are also banned in Victoria.
Institutions such as the National Gallery of Victoria, State Library, and museums are temporarily closed, while the Melbourne Comedy Festival and Food and Wine Festival are postponed.
The Harry Potter musical is also suspended until April 12.
But exclusions to the mass gathering ban include schools, airports, public transport, health services, emergency services, aged care, prisons, parliament, markets, and building sites.
Gaming mogul Crown casino will continue to operate its floor, although Premier Andrews said some of their machines have been turned off to reinforce social distance.
Other events of more than 500 people that were scheduled to happen at Crown have been called off.
Victorian Chief Health Officer Brett Sutton argued the decision not to close schools was based on how the disease presented with children and the risk of pulling people out of health and emergency services to care for kids at home.
“For children under nine years of age, it is an extremely mild disease, and there are virtually no reports of deaths for those below 20, it’s a tiny percentage,” Sutton said.
“My kids are in primary school and in childcare and I’m very happy for them to be there. If I apply evidence otherwise I will apply to my own family […] the appropriate course of action.”
“That applies to hoarding as well. I’m not going crazy with my shopping, I’m buying a few more things as I go shopping routinely.”
Andrews said while it was sensible for people to stock up on one or two extra staples in their regular food shopping, it was not appropriate to buy several weeks’ worth of supplies.
“All that means is those who are vulnerable, people who can’t go to four different supermarkets to get what they need will miss out,” Andrews said.
“We have got care packages, we will get those to you in the event that you run out of those basics.”
He added it would be very unusual to shut down specific areas because of clusters of virus cases.