As public policy, TABOR is bad enough. The legislature, though, could always ask the people to repeal it. However, in 1994, another initiative limited future constitutional amendments to a "single subject." Since TABOR covers such a wide area of revenue policy, it thus can no longer be repealed except by a laborious string of statewide referenda.

In other words, the controls are now smashed. Colorado's legislature can no longer effectively govern, and can't even effectively ask for authority to do so. This is the most radical limitation on state taxing authority anywhere in the country.

The plaintiffs in Kerr, a group of present and former legislators and officials, argue that this radical change violates the Guaranty Clause of the U.S. Constitution, Article IV § 4. The Clause requires the United States to "guarantee to every state in this union a republican form of government." Whatever a "republic" is, the plaintiffs argue, it must have power to tax and spend funds for the public benefit. TABOR, in effect, takes Colorado out of its status as a state.

Guaranty Clause cases are rare; even more rare, Kerr survived the state's motion to dismiss in district court. Colorado argues that these plaintiffs have no business suing and that the federal courts have no business deciding the issue. The result could have important implications for future cases under the clause.

Briefs in the case were filed with the Tenth Circuit this spring. If constitutional law is a matter of consulting the Framers, then the plaintiffs in this case have by far the better argument. Their briefs are richly loaded with quotes from the country's founding era emphasizing that a republic must have a sovereign legislature with authority to govern -- and tax -- independent of transient popular majorities. In Federalist 63, they point out, Madison was at pains to make clear that "republican government" meant government by elected representatives, with "the total exclusion of the people, in their collective capacity," from the power of individual decisions. In Federalist 30, Hamilton explained that a complete power of taxation was required for the survival of republican government: "How is it possible that a government half supplied and always necessitous, can fulfill the purposes of its institution, can ... support the reputation of the commonwealth? ... How will it be able to avoid a frequent sacrifice of its engagements to immediate necessity?"

The state's brief, by contrast, suggests that a "republican" government means virtually nothing. At most, they conceded, it means that a state can't have a king, a dictator, or permanent rule by martial law. I think that's pretty thin gruel as a definition. The state's argument is stronger when it suggests that citizens, even members of the legislature, have no standing to bring a Guaranty Clause challenge, because "[t]he Guarantee Clause ... create[s] rights and obligations between the United States and the State of Colorado."