Last place we were in was a flat (owned leasehold by the OH).
We had a letter from the management company acting on behalf of the freeholder stating that pets should be removed from all properties in the development immediately
Completely ignored it as wholly unenforceable, besides everyone in the other flats nearby f****g loved our cat. (all the other cat owners in the development ignored it as well)
Appreciate the people in question are the tenants but the landlord (leaseholder) can ignore the rule, assuming nothing is written into the leasehold. Whether they choose to or not is another matter.