how would SIN office help?Report the business that is employing them without status. https://www.canada.ca/en/revenue-agency/programs/about-canada-revenue-agency-cra/suspected-tax-cheating-in-canada-overview.html
Contact SIN office out of concern that SIN seems to have not been cancelled although it may have and he is not using it.
CBSA has to deal with a lot of people without status so they prioritize the most dangerous and the larger issues like consultants committing fraud, people trafficking and business getting into illegal schemes like cash in exchange for jobs. These cases take a very long time to gather evidence for so they can hopefully secure a conviction.
Couldn't the person lie and say they have implied status?
Because the SIN office wouldnt have access to the person transcript to see if they attended school or not