Chennai, Oct. 26: M. Karunanidhi today exhorted all chief ministers to join Tamil Nadu’s battle against last week’s Supreme Court ruling that endorsed a 50 per cent ceiling on reservations.

The Tamil Nadu chief minister wrote to his counterparts to make their governments a party to an apex court case where his state would be defending its overall 69 per cent job and education quota for the scheduled castes and tribes and other backward classes.

He argued that a joint fight would be in the interests of the other states, too, for they would also be protecting their own quanta of reservation. Karunanidhi wrote the SC/STs and backward classes together made up over 70 per cent of the population in most states.

In a ruling on October 19, the apex court not only backed an earlier verdict capping reservation at 50 per cent, it also extended the concept of the “creamy layer” to the SC/STs, saying the well- off among them should be denied quota in government jobs.

The Tamil Nadu Reservation Act of 1994 does not exclude the creamy layer. It was pushed through by Karunanidhi’s rival Jayalalithaa when she was in power, and was later included in the Ninth Schedule of the Constitution to give it immunity from judicial review.

But an NGO, Voice Consumer Care, has still questioned the act’s constitutional validity, and its petition will be heard by a nine-judge constitution bench on October 30.