Dr Lorcan Sirr says the measure will be hard to undo
Rent caps come into effect for Cork and Dublin today.
President Michael D Higgins signed the legislation on Friday.
It will see the annual increase being limited to 4%.
The Planning and Development (Housing) and Residential Tenancies Act 2016 takes legal effect immediately, and aims to help ease "rent pressure zones".
The caps could be introduced to other cities and commuter areas from next month, after inquiries by the Residential Tenancies Board Ireland (RTB).
Lecture in Housing Studies, Dr Lorcan Sirr, says it will bring a level of certainty for tenants and landlords.
"The difference that they're going to make is that they will introduce a degree of certainty for tenants and indeed for landlords...so they will know over the next three years exactly how much their rent is going to rise by.
"Whereas previously we had two-year intervals between rent reviews, in the rent pressure zones of the four local authorities in Dublin and Cork city these are going to be annual rent reviews".
"The most significant aspect of this is the actual introduction of some sort of measure to cap rent rises.
"It's going to be very difficult for any government to row back on this in the future - even if the 4% number may fluctuate, the very principle of controlling rents in specific areas is now there and will be very hard to remove in the future".