Jayachandradas was arrested yesterday for posting derogatory remarks on a Facebook page in response to a photo posted by another user of the late leader's statue being guarded by an iron grill at suburban Tambaram.
He had also made some remarks against traders following which a local leader of a traders' association filed a complaint, police said.
Cases have been registered under Information Technology Act and IPC section 505 (statements conducing to public mischief), they said.
Kamaraj, a noted leader in the state, is credited with ushering in a lot of welfare initiatives, including the noon meal scheme for school students, when he was the Chief Minister from 1954-63. He is also popular among the traders.
In some parts of the state, statues of certain leaders are given such protection in order to save them from any act of vandalism.