India, June 23 -- The control of the Trinamool Congress (TMC) slipping from Mamata Banerjee in Bengal, six of nine MPs of Uddhav Thackeray's Shiv Sena (UBT) going to Eknath Shinde's Sena in Maharashtra, seven AAP MPs switching to the BJP in Delhi and Punjab - defections are unfolding in almost all regions of India at once. And a case most likely to decide who avoids the anti-defection law is from the beach state of Goa, pending in the country's top court.

All of these upheavals in Opposition parties, taking the defectors to PM Narendra Modi's BJP-led NDA side, come with the same question of constitutional law. That is, what are the exceptions to the anti-defection law in the Tenth Schedule of the Constitution?

In April, seven of AAP's t...