The Canadian Border Services Agency (CBSA) may choose to detain a foreign national or permanent resident if there are reasonable grounds to believe that he or she:
is inadmissible to Canada and is a danger to the public,
is unlikely to appear for a hearing or removal, or,
has not established his/her identity.

A permanent resident or foreign national may also be detained when entering Canada if this is necessary to conduct examinations, or if there are reasonable grounds to suspect that he or she is inadmissible to Canada on grounds of security, violating human or international rights, or criminality.