Ultra vires

"beyond its powers" - usually in the context of a corporation or governmental authority exceeding the powers and objects as set out in its memorandum and articles of association or charter. Also of some relevance also to a Trust.

These days a rather old fashioned notion as far as a corporation goes - in most sensible jurisdicitons it has been partly or entirely ruled out by legislation, but it is liable to induce butterflies if one is dealing with a local authority.