noun
vested rights
Legal and political term referring to rights already acquired and protected from being taken away.
既得権を侵害するような法律は違憲とされた。
Laws that infringe upon vested rights were ruled unconstitutional.
既得権益 is a broader term meaning 'vested interests', encompassing both rights and benefits, while 既得権 focuses specifically on the rights themselves.
Compound of 既得 (already acquired) and 権 (right). The exact historical derivation is uncertain; the term is a modern legal concept.