Not only is the federal constitution in itself a limitation on state power, in so far as the exercise by the federal government of the powers conferred upon it are inconsistent with any exercise by the state of authority in conflict with that of the federal government as to matters coming within its legitimate scope, but it was deemed necessary in some respects definitely to limit the powers of the state governments, or to prohibit their exercise of authority in ways inconsistent with the general purpose of forming a national government. Therefore it is expressly provided (Art. I, § 10) that "no state shall enter into any treaty, alliance, or confederation; grant letters of marque and reprisal; coin money; emit bills of credit; make anything but gold and silver coin a tender in payment of debts; ... or grant any title of nobility "; and further, that " no state shall without the consent of the Congress, levy any imposts or duties on imports or exports, except what may be absolutely necessary for executing its inspection laws," etc., nor, " without the consent of Congress, lay any duty of tonnage, keep troops or ships of war in time of peace, enter into any agreement or compact with another state or with a foreign power, or engage in war, unless actually invaded, or in such imminent danger as will not admit of delay." Further consideration will be given to these limitations in connection with the discussion of particular branches of the federal power, but they must properly be borne in mind here as indicating the intention to subordinate the authority of the state to that of the federal government in national matters.

The relation of the states to each other is also in some respects regulated by the federal constitution. The prohibition noticed in the preceding paragraph as to agreements or compacts would prevent any attempt being made by two or more states, through concerted action, to interfere with national authority; and would indicate the intention that, while each state in itself is recognized as having powers of government, the relations of the states to each other, and of each to the citizens of each other, are to be determined by the federal constitution, and not by mutual arrangement. But there are further specific provisions as to the relations between the states. Thus, in Article IV it is specified that " full faith and credit shall be given in each state to the public acts, records and judicial proceedings of every other state"; that "citizens of each state shall be entitled to all privileges and immunities of citizens in the several states "; and that fugitives from justice, fleeing from one state to another, shall be surrendered back by the latter on demand of the chief executive authority of the former. These clauses must also be more fully considered in another connection (see below, ch. xxxiii), but are important here as indicating the nature and scope of the federal plan.