India, June 15 -- Twenty rebel Trinamool Congress lawmakers declared to the Lok Sabha Speaker on Sunday that they had merged with a party that holds not a single seat anywhere in India.

The move, apparently to avoid triggering the anti-defection law, has become one of its contested clauses. It was the second time this question was raised this year, just weeks after seven Aam Aadmi Party MPs made a near-identical move in the Rajya Sabha.

Whether the gambit holds will depend less on political arithmetic and more on a legal question the Supreme Court has yet to definitively answer: can a group of legislators declare a merger on their own, or does the political party they represent have to agree?

India's anti-defection law was introduced t...