Private Law Theory

ABSTRACT
Long after Erie abandoned the myth of the common law’s neutrality, the Court continues to treat common law distributions as though they involve no ‘state action’. The Court thus fails to extend constitutional scrutiny to property or contract rights that affect access to constitutional freedoms, provoking harsh critiques from Cass Sunstein and the broader Critical Legal Studies movement. This paper offers a new and rehabilitative perspective on the Court’s indifference to the common law baseline, grounded in John Stuart Mill and Harriet Taylor Mill’s ‘uncertainty principle’ (the ‘harm principle’, reimagined). In On Liberty, the Mills exempted ‘incidental regulations’ from scrutiny under their principle of liberty because such regulations do not expend resources that need to be cost-benefit justified. The Mills argued, for example, that while the government may not prohibit harmless drunkenness, regulators should impose ‘sin taxes’ on alcohol, as long as such taxes are incidental to the unavoidable project of raising revenue. My argument here is that the constitutional implications of common law regulations are often ‘incidental’ in precisely this sense. For instance, Mark Zuckerberg’s legal power to prohibit my speech on Facebook, which originates from his property right in Facebook’s algorithm, is incidental to the necessary project of empowering speech forums to function. Because Facebook would collapse if everyone could tinker with its algorithm, some one must have an exclusive legal power to control it. The property right’s implications for my speech, then, are merely incidental to the independent project of ensuring that Facebook can function. Importantly, when common law regulations are not incidental in this sense, the Court scrutinizes them. Defamation torts and restrictive covenants, for example, have no purpose independent of their infringements of protected constitutional rights (speech and equality, respectively). Ultimately, then, the distinction between incidental and direct regulation provides a powerful descriptive model of current constitutional treatments of the common law.

Moncrieff, Abigail R, The Uncertainty Principle and the Common Law Baseline (December 12, 2025).