The Anti-Defection Law, enshrined in the Tenth Schedule of the Constitution (added by 52nd Amendment, 1985), prevents elected representatives from switching parties after elections. The presiding officer (Speaker/Chairman) acts as the deciding authority on defection cases. Key provisions include disqualification for voluntarily giving up party membership, voting against party whip, and nominated members joining parties within six months. Recent Supreme Court cases like Kihoto Hollohan (1992), Nabam Rebia (2016), and Keisham Meghachandra Singh (2020) have clarified the scope, timing of decisions, and judicial review limits.

The Anti-Defection Law addresses the problem of political instability caused by frequent party-switching by legislators seeking personal gains. Under Article 102(2) and 191(2), the Speaker/Chairman has quasi-judicial powers to decide defection cases, but their decisions are subject to judicial review only on grounds of mala fides, perversity, or violation of constitutional mandate. The law recognizes exceptions like mergers (when 2/3rd of party legislators join another party) and splits (original provision, now deleted). The Supreme Court has established that defection decisions must be made promptly, ideally within three months, and that the Speaker cannot indefinitely delay decisions to protect the government. However, the law has faced criticism for giving excessive power to Speakers who often belong to the ruling party, creating potential conflicts of interest. Recent cases have highlighted issues like the timing of resignations versus disqualification orders, and whether Speakers can decide on defection after losing office.