It's been quiet in the ongoing saga of Kerr v. Hickenlooper, a Guarantee Clause challenge to Colorado's requirement that legislative tax increases be approved by popular vote. The United States Supreme Court remanded the case in light of Arizona State Legislature v. Arizona Independent Redistricting Commission, which concluded that the state legislature of Arizona did have standing to bring a challenge to the authority of an independent redistricting commission. As I noted a year ago, "This, I think, portends poorly for the legislators" bringing the claim here, because they brought their claim as individual legislators, not as the institution of the state legislature.
Sure enough, on remand, the Tenth Circuit concluded the same on Friday. "We now conclude that these individual legislators lack standing because they assert only an institutional injury." The opinion tracks the argument in Arizona State Legislature--and, in my view, the argument that should have been successful even before that case.