David Gamage (Missouri) and John Brooks (Fordham) have a new piece on SSRN, forthcoming in the Tax Law Review, “The Federal Taxing Power in Its New Constitutional Era.” Here is the abstract:

A paradox now sits at the heart of constitutional tax law. Recent jurisprudence culminating in Moore v. United States has presumably revived the realization requirement as a constitutional constraint while also reaffirming that income taxes rest on Article I’s excise power. Those commitments reflect potentially competing conceptions of the federal taxing power: one seemingly limiting Congress through realization-tied definitions of “income,” the other treating excises as a broad category that can reach wealth-adjacent tax bases, potentially including unrealized income. This recent jurisprudence leaves both many long-standing tax provisions and major reform proposals on uncertain constitutional ground.

This Article synthesizes this jurisprudence to describe a theory of the taxing power for this new era. We argue that sense can be made of the competing lines of cases by seeing the key constitutional questions as structural, not definitional: first, whether a tax provision targets a proper excise subject—an activity, transaction, or institutional participation distinct from ownership as such—and, second, whether statutory design keeps liability bounded to and satisfiable from that taxed base. We develop these questions through our proposed Base-Tether framework, an interpretive reconstruction that synthesizes the anti-detachment intuition from Moore and Eisner v. Macomber with the long line of excise tax cases. While we view the taxing power at the founding as originally broader than this, we are undoubtedly now in a new constitutional era that scholars, attorneys, and policymakers must take seriously. The Base-Tether framework supplies drafting and litigation guidance for navigating the post-Moore minefield of uncertainty as to which tax provisions are constitutionally vulnerable.