You can find this in many places at the CIC website but for example here:
http://www.cic.gc.ca/english/information/applications/guides/5445ETOC.asp#appendixA
or here:
http://www.cic.gc.ca/english/information/applications/guides/5445ETOC.asp#appendixA
or here:
This part proves that they can not deny you entry at the border as long as you have not officially lost your status somehow. Even if they believe that you do not meet the residency requirements, they still have to let you in and may decide to report you which however doesn't seem to be very common based on other peoples experience:http://www.cic.gc.ca/english/resources/manuals/enf/enf04-eng.pdf - page 37 said:11.12. Residency obligation for permanent residents
A28(1) states that a permanent resident must comply with the residency obligation with respect to every five-year period. A28(2) stipulates that a permanent resident complies with this obligation if, on each of a total of 730 days in that five-year period, they are:
• physically present in Canada;
• outside Canada but accompanying a Canadian citizen spouse or common-law partner or, in the case of a child, their parent;
• outside Canada employed on a full-time basis by a Canadian business or in the public service of Canada or of a province;
• outside Canada accompanying a permanent resident spouse or common-law partner or, in the case of a child, their parent, who is employed on a full-time basis by a Canadian business or in the public service for Canada or a province; or
• able to meet other conditions for compliance that are set out in the Regulations.
http://www.cic.gc.ca/english/resources/manuals/enf/enf04-eng.pdf - page 34 said:BSOs can refuse entry to a permanent resident only when the person has already lost the status in accordance with the provisions of A46 (such as a final determination has been made that they have failed to comply with the residency obligations or when a removal order comes into effect). In other words, once a permanent resident’s status is established, the person may enter Canada by right and the immigration examination under IRPA concludes.
However, BSOs will sometimes become aware of evidence of non-compliance with the residency obligation in the course of the determination that a person is a permanent resident. When BSOs believe that a person who they have determined is a permanent resident is in non-compliance with the residency obligation of A28, the BSO may explain to the person that it has been established that they have a right to enter Canada, that there is some reason to believe they could be the subject of a report under IRPA which could lead to the issuance of a removal order, and that although the person may now enter Canada, they may choose to answer additional questions to determine whether the BSO's concerns are well founded or not.