“15. A “necessary party” is a person who ought to have been joined as a party and in whose absence no effective decree could be passed at all by the court. If a “necessary party” is not impleaded, the suit itself is liable to be dismissed. A “proper party” is a party who, though not a necessary party, is a person whose presence would enable the court to completely, effectively and adequately adjudicate upon all matters in dispute in the suit, though he need not be a person in favour of or against whom the decree is to be made. If a person is not found to be a proper or necessary party, the court has no jurisdiction to implead him, against the wishes of the plaintiff. The fact that a person is likely to secure a right/interest in a suit property, after the suit is decided against the plaintiff, will not make such person a necessary party or a proper party to the suit for specific performance.”
Supreme Court
Mumbai Intl Airport Pvt Ltd vs. Regency Convention Centre & Hotels Pvt. Ltd. & Ors., (2016) 2 SCC 779