The activists are squatting on the road side near the High Court junction holding banners and placards proclaiming "in democracy people are supreme" and "Judges sitting in glass houses should not throw stones at people".
About 2000 police personnel led by Kochi Police Commissioner M R Ajith Kumar are camping in the area.
The Police Commissioner had yesterday issued a notice to CPI(M) Secretary Pinarayi Vijayan asking the party not to disturb the functioning of the court by holding demonstrations.
Party sources said the dharna would conclude at 1700 hrs.
The High Court had last week sentenced Jayarajan to six months imprisonment for his derogatory comments against two judges for the court verdict on banning roadside meetings.
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