*vested interest*

. 1. a special personal interest, usually financial, in an existing system, law, or institution, which hinders a person from making objective decisions regarding that system, law, or institution. A vested interest may be one which benefits a relative, or, in an extended sense, one which defends a person's own reputation or previously expressed views. [ PJC ]

2. a right given to an employee by a pension plan, which cannot be taken away. [ PJC ]

3. pl. the persons, corporations, or other groups which benefit most (usually financially) from the existing system of institutions, laws, and customs. [ PJC ]