Via Derek Muller at Excess of Democracy, last week the Tenth Circuit found a guarantee clause claim justiciable. Here is the opinion in Kerr v. Hickenlooper, which is challenge to Colorado's constitutional limits on the legislature's power to tax. Additional thoughts from Garrett Epps at The Atlantic: Can the U.S. Government Declare a State Constitution "Un-Republican"?
Previous thoughts on this case from Derek Muller are here (and from me here and here). I earlier argued that the case is a non-judicial political question:
A proper textually founded political question doctrine arises not from some vague idea that the case is too hard (or too embarrassing, or too controversial) but -- as in Nixon [v. United States] -- the idea that the decision is textually committed to another branch (that is, committed by the particular phrasing of the clause at issue).
That seems to be the case with the guarantee clause. It provides:
"The United States shall guarantee to every State in this Union a Republican Form of Government . . . ."
This reads like an obligation placed on the political branches of the U.S. government, not the judiciary. It would be a different matter if the clause had used language parallel to Article I, Section 10, whose prohibitions on the states, expressed as direct legal commands, are clearly justiciable; it might have said: "no State shall have anything but a republican form of government." That would sound too like an ordinary legal command, and it would not become any less so simply because there might be some ambiguity in the word "republican." But the awkward and indirect phrasing of the guarantee clause suggests that it is not an ordinary legal obligation placed on the states for the courts to enforce. Rather, it is a guarantee effectuated through political action of "the United States" as a whole -- and a potentially powerful one: as a result of the clause, for example, Congress could overturn non-republican aspects of state governments (and courts would enforce such laws).
Nothing the court says changes my mind a bit. Here is the core of the court's textual argument:
The text of the Guarantee Clause does not mention any branch of the federal government. It commits the “United States”—which would normally be read as including the Article III courts—to the preservation of republican government in the states. The Guarantee Clause is found not in Article I or Article II, where we would expect to find it if its provisions were textually committed to another branch, but in Article IV. Moreover, two other provisions of Article IV specifically empower Congress to act, but the Guarantee Clause does not. See id. § 1 (“[T]he Congress may by general Laws prescribe the Manner in which [public] Acts, Records, and Proceedings shall be proved, and the Effect thereof.”); id. § 3 (“New states may be admitted by Congress into this Union . . . Congress shall have Power to dispose of and make all needful Rules and Regulations respecting the Territory or other Property belonging to the United States.”). The omission of any mention of Congress from the Guarantee Clause, despite Congress’ prominence elsewhere in Article IV, indicates there is no “textually demonstrable commitment”—certainly not an inextricable one—barring our review or district court consideration of this case.
My previous response to the "federal courts are part of the 'United States'" argument is here, and I don't have much to add. The court's point about other clauses of Article IV seems unpersuasive -- the more important text is the rest of Article IV, Section 4, which is obviously not directed to the courts ("The United States ... shall protect each of [the states] against invasion; and on Application of the Legislature, or of the Executive (when the Legislature cannot be convened) against domestic Violence." The absence of a specific reference to Congress only shows that (under some circumstances) the clause is addressed to the President as well. But the main point (which the court doesn't address at all) is that if the Framers wanted to place a direct prohibition on the states, they would have phrased it as in Article I, Section 10 -- where most of the direct prohibitions are -- or as in other clauses of Article IV.
An additional point is this: an open-ended commission to review all state governments to assure they are sufficiently "republican" (surely an imprecise term) is a hugely important power. If the Constitution had been understood to give it to the federal courts, one might expect some discussion and objection at the Founding (which, as far as I know, there was not). Perhaps this only indicates a very broad view of "republican" (such that any state that wasn't a monarchy or a dictatorship would count). But I think it also suggests an understanding that Congress would principally exercise the power (which meant that any exercise of it would have needed the assent of a majority of the state-selected Senators). There is an enormous difference between saying that the political branches of the U.S. government can declare a state's constitution un-republican, and saying that courts can do it.
In any event, this is a hugely important case. If Colorado loses on the merits, it would transform the relationship between the states and the federal judiciary.