Before proceeding with a further discussion of state legislation, it will be convenient to explain the nature of the limitations on that power; for it may be stated as a general proposition that the power of state legislation in the making of laws is controlled only by its own discretion, unless it oversteps the limitations on its power imposed by the state or federal constitutions.

(1) The first limitation is one already suggested, that the power which the legislature attempts to exercise must be legislative in its nature, for it is only legislative power that the state constitution confers upon the legislative department, and it cannot interfere with the other departments in the discharge of their functions. Such limitations, so far as they restrain the legislative department with reference to the executive and judicial departments, have already been sufficiently considered. (See ch. iv.)

(2) It must also be noticed that the legislative department in the enactment of laws must comply with the forms of procedure pointed out by the constitution, for only as authorized by the constitution can a legislature exercise its functions. Something has already been said in preceding chapters as to the constitution and organization of the legislative departments and the methods of exercising their powers so far as they are specified in the state and federal constitutions.

(3) The state legislature is also limited in its powers by the fact that it is subordinate to the federal government as to all matters which by the federal constitution are placed within the control of that government (see ch. iii), and therefore state legislation as to subjects over which the federal government has exclusive supervision will be invalid; and even as to subjects which are within the scope of federal regulation, although the powers of the federal government are not exclusive, state legislation must yield to such federal regulations as have properly been adopted with reference to such subjects.

(4) The state legislature is restricted by the direct limitations upon its power found in either the state or federal constitution. The more general and important of these are that no person shall be deprived of his life, liberty, or property without due process of law; that no person shall be denied the equal protection of the laws; that the obligation of contracts shall not be impaired; that private property shall not be taken for public use without compensation; and that no bills of attainder or ex post facto laws shall be enacted. These express limitations will be considered in subsequent chapters. The discussion of these limitations constitutes the principal part of constitutional law as administered by the courts.

(5) A legislature cannot bind or restrict the powers of subsequent legislatures, except in so far as it may and does create contractual obligations as against the State. (See below, § 268.)