The Supreme Court on Thursday ruled that claims of partisan gerrymandering are beyond the reach of the federal courts, delivering a sharp blow to challengers who hoped the justices would endorse a standard for determining when a map is so infected with politics it violates the Constitution.

The court split 5-4 along ideological lines, with Chief Justice John Roberts writing for the conservative majority. The ruling, in two cases involving voting maps from Maryland and North Carolina, effectively forecloses the courts to hearing future partisan gerrymandering claims.