It says in the terms:
If the landlord did not give the notice at the time the lease was entered into, the new lesser may, within 2 months of the beginning of the lease, apply to the regie du logement to have his rent fixed
你的房客几经住了多于一年,所以他已经超过了2个月
可是,it also says:
The lessee may also make such application to the regie du logement within 2 months of the day he becomes aware of a false statement in the notice.
我建议你问一下regie du logement, 我个人认为你的房客没有权利这样做。不过最好得到权威意见,在回复他们。