The judicial power shall extend to all cases,[1] in law and equity,[2] arising under this constitution, the laws of the United States, and treaties made or which shall be made, under their authority;[3] to all cases affecting ambassadors, other public ministers, and consuls;[4] to all cases of admiralty jurisdiction;[5] to controversies to which the United States shall be a party;[6] to controversies between two or more states;[7] between a state and citizens of another state;[8] between citizens of different states;[9] between citizens of the same state claiming lands under grants of different states;[10] and between a state or the citizens thereof, and foreign states, citizens or subjects.[11]_

[1] The courts decide what the law is, whether a specified law is constitutional or not, and what the meaning of constitutional provisions is, but only as these questions arise in cases brought before them for trial.  They do not advise congress or the president as to the constitutionality or unconstitutionally of a law.  They do not directly make law.  But in determining the meaning of certain laws and of constitutional provisions they may determine what the law is, and thus they may be said to make law indirectly.  But sometimes a legal question or a question as to the meaning of a constitutional provision remains for a long time unanswered, because no case involving the question comes before the courts.

[2] Sometimes the law provides no adequate remedy for a wrong.  Here is the necessity for a court of equity.  For instance, A sells his business to B, agreeing not to become a rival, but immediately reopens in the next block.  B’s only remedy in law is to secure damages.  If this remedy is shown to be inadequate, a court of equity will close A’s store.  Or if C, having contracted to do a certain act for D, fails or declines to perform his part, the law can only award D damages; equity will compel the fulfillment of the contract.  Law is curative, equity is preventive. (See Dole, 502.)

In some states there are separate courts of law and of equity.  But the provision under discussion gives the United States courts jurisdiction in cases both of law and of equity.  “There are no juries in equity cases, and no criminal trials.”

[3] These pertain to the whole United States, so cases arising under them should be tried by a national, not by a state, court.

[4] Thus showing respect for the governments represented by them.

[5] That is, to cases arising on the high seas or on navigable waters.  These matters, according also to I. 8:  10, 11, are under the jurisdiction of the United States, and therefore this provision is simply a consequence of the two referred to.

[6] Because then the interests of the whole country are at stake, and should not be left to any state.

[7] Because the United States was organized to “insure domestic tranquility.”