President Iohannis has intervened amid concern over plans to introduce pardons and decriminalise offences in corruption cases.
Thousands of Romanians have protested in Bucharest over government plans they fear could weaken an anti-corruption drive.
Draft decrees show an intent to pardon convictions of less than five years for several crimes. The government also wants to decriminalise abuse of power if it causes prejudice worth less than 200,000 lei (around 44,000 euros).
In Bucharest an estimated 3,000 people marched on a government building. Other smaller protests were reported in the western city of Cluj, as well as in Sibiu, Iasi and Craiova.
The demonstrators fear the measures will be used to enable politicians to escape convictions for corruption and get out of prison.
Romania’s President Klaus Iohannis has intervened, attending his first cabinet meeting since taking office in 2014. He warned against the plans which he described as “elephants in the room” that no-one was talking about.
President Klaus Iohannis went to a government meeting for the first time just to make sure that ordinances on… https://t.co/wc0KfgZWqu— Romania-Insider.com (@romania_insider) January 18, 2017
The government, which took office in December, has said it needs to get the criminal code in line with recent court rulings and argues that pardons could help ease prison over-crowding.
But legal officials have criticised plans to change the law without consulting the judiciary or going through parliament.
Abuse of power is said to account for a third of anti-corruption investigations.
The European Commission, which has Romania’s legal system under special monitoring, has praised judges’ efforts to fight corruption but is alarmed at politicians’ attempts to try to weaken investigations.
The new Government moves on with controversial measures related to the justice system. https://t.co/m2pmIU5zWH— Romania-Insider.com (@romania_insider) January 18, 2017