Generally, a landlord cannot change the locks or otherwise exclude you from your rented home without lawful authority, even if rent is owed or there is a dispute. A lockout may amount to an illegal eviction; giving notice to end a tenancy does not normally allow the landlord to remove you or your belongings without following the proper process. If the locks have been changed, keep evidence, avoid forcing entry, and seek urgent advice from Threshold, a solicitor, or the RTB, while contacting the Gardaí if you feel unsafe. Whether the landlord acted unlawfully and what remedy may be available will depend on the facts and may ultimately be decided through the RTB or the courts.