Also known as: comity · comity of nations · comitas gentium
Written by attorneys · grounded in primary & secondary sources — see below
A principle of mutual deference and respect among sovereigns or courts that discourages one from interfering with the proceedings or laws of another. The principle operates by directing federal courts to abstain from enjoining ongoing state criminal prosecutions absent extraordinary circumstances such as bad-faith enforcement.
Corinne Cho faces an ongoing state criminal trial for market manipulation. She files a federal suit seeking to enjoin the state proceeding on constitutional grounds. The federal court declines to issue the injunction because principles of comity require deference to the state forum absent proof of bad-faith prosecution.
Craig Caldwell sues a union in federal court under federal labor law and adds a related state tort claim arising from the same workplace incident. The court exercises supplemental jurisdiction because the claims share a common nucleus of operative fact and comity does not counsel against hearing the entire controversy in one proceeding.
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Catherine Carter, a nonresident, is served with process while temporarily in the forum state. The court recognizes that comity among sovereigns limits one state's authority to bind persons or property located exclusively in another state without proper jurisdictional contacts.
Colin Chambers operates a vessel engaged in interstate commerce. Two states assert conflicting licensing requirements. The court resolves the conflict by applying principles of comity that respect each sovereign's regulatory sphere while avoiding direct clashes between state laws.
Camila Cervantes challenges a state-funded remedial-education program in federal court on Establishment Clause grounds. The court considers comity concerns before deciding whether to adjudicate the claim or allow state courts to interpret and apply their own statutory scheme first.
Cecilia Cabrera sues the State of Maine for damages in a Massachusetts court. The Massachusetts court dismisses the action because comity among sovereign states prevents one state from exercising jurisdiction over another nonconsenting state in its own courts.
A federal court may decline supplemental jurisdiction when the state claim raises a novel or complex issue of state law, when state claims substantially predominate, or when all federal claims have been dismissed. These discretionary grounds reflect comity and federalism concerns that favor allowing state courts to resolve unsettled questions of their own law.
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No. Each state is a separate sovereign, so the Double Jeopardy Clause does not bar one state from prosecuting conduct already prosecuted by another state. Comity may supply policy arguments for coordination between prosecutors, but it does not create a constitutional bar.
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Comity reinforces the constitutional structure under which one state may not hale another nonconsenting state into its courts for damages. A forum state therefore must dismiss such an action even if the defendant state was engaged in proprietary activity.
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…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…