Guarantee Clause
Article IV, Section 4, known as the Guarantee Clause, commits the United States to guarantee each state a republican form of government and to protect states against invasion. It also provides for protection against domestic violence when requested by a state legislature, or by its executive when the legislature cannot meet. The Supreme Court has generally treated disputes about whether a state government is republican as political questions for the political branches, rather than questions for federal courts to decide.
Article IV, Section 4, known as the Guarantee Clause, commits the United States to guarantee each state a republican form of government and to protect states against invasion. It also provides for protection against domestic violence when requested by a state legislature, or by its executive when the legislature cannot meet. The Supreme Court has generally treated disputes about whether a state government is republican as political questions for the political branches, rather than questions for federal courts to decide.
Example: During Reconstruction, Congress generally had the role of organizing and recognizing new republican governments in the defeated Confederate states as part of carrying out the Guarantee Clause.
Common misconception: A common mistake is to think federal courts routinely use the Guarantee Clause to strike down state laws. The Supreme Court has generally treated such claims as political questions, although it has left open the possibility that not every claim is nonjusticiable.
Sources: Guarantee Clause Generally | Constitution Annotated