In order to declare a public order emergency, the Emergencies Act requires that there be an emergency that arises from threats to the security of Canada that are so serious as to be a national emergency.
Threats to the security of Canada include the threat or use of acts of serious violence against persons or property for the purpose of achieving a political or ideological objective.
A national emergency is an urgent, temporary and critical situation that seriously endangers the health and safety of Canadians that cannot be effectively dealt with by the provinces or territories, or that seriously threatens the ability of the Government of Canada to preserve the sovereignty, security and territorial integrity of Canada. It must be a situation that cannot be effectively dealt with by any other law of Canada.
Any measures taken under the Act must be exercised in accordance with the Canadian Charter of Rights and Freedoms and should be carefully tailored to limit any impact on Charter rights to what is reasonable and proportionate in the circumstances.
https://www.justice.gc.ca/eng/csj-sjc/section58.html