Also known as: ex comitatis · comity · ex comitatu
Written by attorneys · grounded in primary & secondary sources — see below
A principle under which a court or government acts out of courtesy or deference to another sovereign rather than legal obligation.
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Ella Emerson faces state criminal charges for publishing leaked audio. She sues in federal court to enjoin the prosecution on First Amendment grounds. The federal court declines the injunction, acting ex comitate to allow the state proceeding to continue absent bad faith or harassment.
Ella Emerson obtains a child-support order from a Canadian tribunal. She registers it in a U.S. state court that lacks an applicable statute. The court enforces the order ex comitate, treating the foreign decree as valid out of deference to the issuing sovereign.
Elijah Edwards challenges a state regulatory scheme in federal court while parallel state proceedings continue. The federal court stays its hand ex comitate, deferring to the state court's primary role in interpreting its own laws.
Esther Eisenberg sues Arizona in a Colorado court for damages arising from treatment at a state facility. The Colorado court dismisses the action ex comitate, honoring Arizona's immunity from suit in another state's courts without consent.
Emmett Egan challenges a state funding formula in federal court while a related state case remains pending. The federal court abstains ex comitate, allowing state courts to resolve the unsettled state-law question that could moot the federal claim.
Eduardo Enriquez sues a foreign corporation in federal court for events occurring abroad. The court declines jurisdiction ex comitate, respecting the foreign sovereign's interests and the limits of U.S. adjudicative authority.
A court acts ex comitate when it defers to another sovereign out of courtesy, such as by abstaining from enjoining a pending state prosecution or recognizing a foreign support order.
Supporting sources
No. When principles of comity support abstention, a federal court typically stays the federal action to retain jurisdiction while the state court resolves the controlling issue.
Supporting sources
Yes. After the anchor federal claim is dismissed, a court may decline supplemental jurisdiction over remaining state claims out of comity and respect for state courts' primary role in interpreting their own law.
Supporting sources
…an elementary principle, that the laws of one State have no operation outside of its territory, except so far as is allowed by comity; and that no tribunal established by it can extend its process beyond that territory so as to subject either persons or property to its decisions. "Any exertion of authority of this sort…