tion by the Supreme Court
with determined resistance. Consequently, Worcester and Butler remained
in jail until they agreed to abandon further efforts for their discharge
by federal authority in the form of a writ of error, whereupon the
governor pardoned them on the condition that they leave the State.

CONFLICTS OF JURISDICTION: COMITY

Aside from these more dramatic assertions of independence of federal
courts, State court interference with the federal judiciary has occurred
for the most part in conflicts of jurisdiction which affect only the
lower federal courts as courts of concurrent jurisdiction and in
attempts to release persons in federal custody. To the extent that this
phase of federal-state relations is not governed by statute or the
supremacy clause of article VI, it is governed by comity, a self-imposed
rule of judicial morality whereby independent tribunals of concurrent or
coordinate jurisdiction exercise a mutual restraint in order to prevent
interference with each other and to avoid collisions of authority.
Although the Court on one occasion has stated that the principle of
comity is not a rule of law but "one of practice, convenience, and
expediency"[653] which persuades, but does not command, it has also
declared that in the American Federal System it has come to have "a
higher sanction than the utility which comes from concord" and has been
converted into a principle "of right and of law, and therefore of
necessity."[654] As developed and applied by the Supreme Court the rule
of comity is exemplified in three classes of cases: First, those in
which a court has acquired jurisdiction of the _res_ or the possession
of property and another court interferes with that jurisdiction or
possession; second, those in which a court has acquired jurisdiction or
custody of the person and another interferes with such jurisdiction or
custody, most frequently by discharges from custody in _habeas corpus_
proceedings; and, third, those in which injunctions are used to stay
proceedings in another court or to enjoin official action before the
courts of proper jurisdiction have had an opportunity to adjudicate the
issue.

JURISDICTION OF THE _RES_

As applied by the Supreme Court in cases involving concurrent
jurisdiction the principle of comity means that when the jurisdiction of
a court and the right of a plaintiff to prosecute a suit therein have
attached and when a court has acquired constructive possession