Mumbai and Bengaluru, Sept. 21 -- A legal opinion by veteran laywer Sudipto Sarkar has emerged at the centre of the dispute over N. Chandrasekaran's reappointment as Tata Sons chairman, after Tata Trusts challenged the validity of the board's decision.

The Tata Sons board last Thursday approved Chandrasekaran's third five-year term after an independent director's casting vote broke a deadlock between the two Tata Trusts nominees on the board. Noel Tata, chairman of Tata Trusts, voted against the reappointment, while Venu Srinivasan voted in favour.

Noel Tata has called the decision "illegal," arguing that Section 121 of Tata Sons' Articles of Association requires the support of more than half of the Trusts' nominee directors for the cha...