That's one of the reasons why portuguese renting market is so bad. There were rent control policies for like 40 years. It has been phased out but the market still has the signs of its damages.
There also other contributing policies and the policies change almost every two years.
I'm one that could invest in the market, to bring more houses to be rent, but I can not risk 150 000 euros buying a house to rent (middle income market) and then having problems evicting with a non-paying renter, being forbidden to increase the rent due a new law or god help me if I need to use the court system to ask for renter damages.