What happens if the landlord enters the premises when they're not legally able to?

[landy]

any landlord who causes or permits any interference with the reasonable peace, comfort or privacy of the tenant, in the use by the tenant of the premises, is in breach of the agreement. If the circumstances amount to harassment of the tenant, the landlord is liable to a penalty not exceeding $2000.

if a landlord is in breach of the agreement by interfering with the peace, comfort and privacy of the tenant (which is a factual question), the tenant may serve a notice of termination on the landlord to end the tenancy. The tenant could also make an application for an order of the Tribunal (for example compensation for removal costs or similar expenses).

[elklaw]

The landlord can be found in breach and made to pay damages if there is unauthorized entry in a non-emergency situation without tenant consent and approval. The laws of each state will define the type of action and the type of damages that can be pursued.