The government has been pleading with Canadians to self-isolate if they've returned from a trip since mid-March, but this move under the Quarantine Act makes it a legal obligation.
"All Canadians have been working very, very hard to practice physical distancing in their lives, and we have, for some time now, been urgently advising people coming into Canada to self-isolate for 14 days upon their return", said Deputy Prime Minister Chrystia Freeland on Wednesday.
The measures also make it tougher for those facing quarantine to get home, to keep the greater public safer from potential exposure to COVID-19.
The minister also said, "Individuals who exhibit symptoms upon arrival in Canada are forbidden from using public transit to travel to their places of self-isolation".
Before this announcement, some provinces and territories had already introduced mandatory isolation periods for people returning from other parts of the world and even other parts of Canada. "Essential workers are excluded".
"We all really appreciate that it is so important to have this self-isolation to protect the health and safety of Canadians", Freeland said.
And Canada's border with the USA, while closed to non-essential travel, is still open to trade and commerce, as well as travel for cross-border workers or students with visas.
Canada is now testing 10,000 people a day and has tested more than 142,000 people.
Everyone permitted to enter Canada are subject to this Order, "with the exception of certain persons who cross the border regularly to ensure the continued flow of goods and services, and those who provide essential services".
If a designated quarantine officer believes that a traveller has refused to isolate themselves, they can ask a peace officer to arrest the traveller and bring them into quarantine.
The federal Quarantine Act, which was updated in 2005 after the deadly SARS outbreak, gives the federal health minister the power to designate quarantine zones and fine or jail travellers who disobey quarantine orders.