The above answer is incorrect.
the landlord is not legally allowed to tell a tenant who they may have in their apartment.
If the landlord has an issue with the tenant`s guests,
such as damaging property,
then the landlord must abide by the Residential Tenancy Act in the jurisdication they reside.
The landlord must file the appropriate forms with the landlord and tenant board.
If the landlord interferes with a tenants guests this may affect the tenant`s reasonable enjoyment and they too can file an application with the board against the landlord.
Tenants please inform yourself of the rights you have to stop landlords who are in the wrong.