The written instrument agreed upon by the people
of the Union or of a particular state, as the absolute rule of action and
decision for all departments (i.e. branches) and officers of the government in
respect to all the points covered by it, which must control until it shall be
changed by the authority which established it (i.e., by amendment), and in
opposition to which any act or ordinance of any such department or officer is
null and void.