Anyone wanting to enter Canada for a temporary period of time must acquire a Temporary Resident Visa, unless they’re citizens of a country that is visa-exempt. The Canadian Immigration Visa Office, outside of Canada, issues these Temporary Resident Visas. The applicant must fulfill all the requirements for being admitted to Canada as a visitor. However, even if someone has acquired this Visa there is no guarantee that the Citizenship and Immigration Canada Officer will admit them when they reach the border.
When arriving at the Port of Entry everyone visiting must prove that their visit to Canada is just temporary. They will be asked for proof that they have enough money to support themselves during their visit. A criminal background check may also serve to deny someone entrance to the country. And finally, certain medical conditions or health concerns may prevent someone from passing through the Port of Entry to Canada.