PMM said:
Actually Vegreville or Mississauga does a criminal name check on sponsors to see if they are criminally barred from sponsorship.
This is because there are a few grounds upon which sponsors may be ineligible to sponsor (e.g., previous domestic violence charges).
On November 17, 2011, new eligibility requirements for sponsors came into force. These new requirements prevent a person from sponsoring a member of the family class if they have been convicted of certain offences.
Source: http://www.cic.gc.ca/english/immigrate/sponsor/spouse-apply-who.asp
But this is done by CIC, the sponsor doesn't need to do this.