The Riga Northern District Court gave the decision, which is subject to appeal within ten days, the BNS newswire reported.
Usakovs' lawyer Artis Vidzups had asked the court earlier to drop the case, arguing that views expressed on his personal social media accounts did not constitute electioneering, which runs contrary to Latvia's strict ban on political messages in the day before voting takes place.
"There is no law banning me from voicing my personal opinion in my personal accounts on social networks Twitter and Facebook either on the day before the elections or the election day. In the same way I might have told my relatives, acquaintances or neighbors which list they should vote for," Usakovs, leader of the Harmony political party told BNS.
Later - ironically enough via his Twitter account - he made light of the language in which the court proceedings had been couched, saying "What's a 'tvit'?"
Kas ir "tvits"? No tiesas sprieduma. Vienkārši fantastiski :))) pic.twitter.com/U1GnCBNWoX— Nils Ušakovs (@nilushakov) January 5, 2015
In December Prime Minister Laimdota Straujuma of the Unity party fell foul of the same law after telling journalists on election day that she hoped Harmony wouldn't win many votes: a rather obvious statement from the leader of a rival party, bit still enough to land her with a €50 fine of her own.