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 navig