Geoffrey McGovern and Jonathan Krasno have posted this draft on SSRN. Here is the abstract:

The Supreme Court’s inability to define substantial over breadth reveals conceptual flaws in a core component of First Amendment law. We argue for a new approach to over breadth that takes cognizance of the empirical nature of the question. The article advances overbreadth scholarship by articulating a means – both empirically plausible and theoretically valid – for applying the overbreadth doctrine in a more routine, measurable, and administrable fashion. In Part I we derive three doctrinally supported measures of statutory imprecision. We establish that only one closely comports with First Amendment goals, is stable in different test scenarios, and provides a substantive measure of statutory sweep. In Part II we empirically examine measurement’s central role in a landmark over breadth case, McConnell v. F.E.C., showcasing the pressing need for a definitive standard for measuring over breadth. Our preferred metric remedies the Court’s repeated errors by more clearly providing guidance to lower courts and litigants, while closely tracking the over breadth doctrine’s important First Amendment goals.

For anyone who was involved in the BCRA/McConnell wars over the overbreadth issue in BCRA’s electioneering communications standard, this paper, co-authored by one of the Brennan Center researchers on the original Buying Time study, is not to be missed. Though there are parts of this paper (or at least the earlier draft that I read over the summer) that I disagree with, the paper provides an important framework for conceptualizing the differing meanings of overbreadth. This paper could turn out to be quite important for the courts in refining the overbreadth doctrine, and more broadly than in the campaign finance field.