term:

Usurp

usurp vb

[Latin usurpare to take possession of without a strict legal claim, from usus use + rapere to seize]
vt
: to seize and hold (as office, place, or powers) in possession by force or without right [the courts may not the powers of the legislature]
vi
: to seize or exercise authority or possession wrongfully
usur·pa·tion [yü-sər-pā-shən, -zər-]
n

usurp·er [y-sər-pər, -zər-]
n

Source: Merriam-Webster's Dictionary of Law ©1996. Merriam-Webster, Incorporated. Published under license with Merriam-Webster, Incorporated.