All businesses operating in Canada are affected and restricted by the Personal Information Protection and Electronic Documents Act (PIPEDA). As stated in the Frequently Asked Questions section of the Privacy Commissioner's Website, "Once an organization or landlord has collected any personal information, it takes on new risks and responsibilities under PIPEDA. PIPEDA requires any private organization that collects your  personal information to also protect it against unauthorized loss, theft or disclosure. Because credit bureaus—which are used by many landlords—collect, use and disclose personal information through their consumer credit reports, they are also governed by provincial and federal privacy laws. " Disclosing information about a current or prior tenant to others requires that person's written consent. Here is a link to a Privacy Commissioner's report regarding a complaint about an organization that maintained a bad tenant list and distributed information to others, without their consent. http://www.priv.gc.ca/en/opc-actions-and-decisions/investigations/investigations-into-businesses/2016/pipeda-2016-002/. There may also be provincial statutes that also impact on the concept of "Bad Tenant" lists, but overall we usually ask that landlords focus their attention on dealing directly with other landlords who understand and use up to date and PIPEDA-safe rental applications and leases, in order to avoid allegations of privacy abuse by would-be tenants. Sharing information about tenants in the context of screening after proper consent has been obtained is the most effective way to approach this issue.