The social-democratic govt. of PM Sorin Grindeanu published two emergency decrees on Wednesday that will set free inmates.
The social-democratic government of Prime Minister Sorin Grindeanu published two emergency decrees on Wednesday that will set free inmates serving sentences of up to five years for non-violent crimes.
If the decrees are adopted, about 2,500 people, including several elected officials and magistrates who are behind bars after being convicted of corruption, will be released.
Grindeanu wants to implement the measures through emergency ordinances that would bypass parliament and would not require Iohannis' signature.
"Several political officials who have judicial issues want to change the legislation and weaken the rule of law," Iohannis said, as he stood among protesters in Bucharest.
"It is unacceptable to modify the law so that the cases of dozens, even hundreds, of politicians, are wiped out," he added.
Justice Minister Florin Iordache defended the proposals, saying they would help unburden overcrowded jails.
Iohannis was elected in November 2014 under an anti-graft platform and urged politicians to stamp out entrenched corruption in one of Europe's poorest countries.
After his election, he said he wanted a graft-free country when his term ends in 2019.
On Wednesday, Iohannis attended a government meeting in the hope of stopping the decrees from being adopted.
Protesters gathered near University Square in downtown Bucharest before marching to the government building, chanting "Resign" and "Democracy, not amnesty".
"Why do they want to pass these laws now if not to save political officials under investigation or already sentenced?" protester Liana Dumitrescu, 74, told AFP. "They have to be stopped."
In the western city of Cluj, more than 5,000 people protested against the government's willingness to "pardon corrupt political officials".
About 3,000 protesters also flooded the streets of Romanian cities Brasov, Timisoara, and Iasi.
Dumitrescu referred to the case of Liviu Dragnea, the social-democratic leader, who was given a two-year suspended sentence for vote-rigging. He is currently on trial for abuse of power.
The measures have been heavily criticised by numerous organisations and several Romanian officials and institutions, including the attorney general Augustin Lazar, anti-corruption chief prosecutor Laura Codruta Kovesi, and High Court president Cristina Tarcea.
In its 2015 annual report, the European Commission, which is closely monitoring justice reforms in Romania, had warned against any proposals that sought to "pardon individuals convicted on corruption charges".