In the universe of legal restrictions subject to judicial review, those characterized as fully denying some aspect of a constitutional right—bans—are often subject to per se rules of invalidity. Whether the subject of the restriction is a medium of expression, the valuable use of property, or a class of weapons, courts in such cases will often short-circuit the standard doctrinal machinery and strike down the law, even if it might have survived heightened scrutiny. Identifying laws as bans can thus provide an end run around the tiers of scrutiny and other familiar forms of means-ends analysis. And yet it is surprisingly difficult to identify what makes a law a ban and why that characterization should matter. Why are yard signs an “entire medium of expression” or assault weapons an “entire class of ‘arms’”? Why does it matter if they are completely prohibited? If the ban label is to have such important constitutional consequences, these questions must be brought to the fore. Using the emerging jurisprudence of the Second Amendment as an illustration, this Article explores functional, formal, and purposivist answers. It argues that none of these answers can avoid judicial discretion in the way that some proponents of rules-based jurisprudence might wish. But the ban framework might nonetheless be defensible in a limited set of cases, especially on functional grounds, as a shorthand for the conclusion that a challenged law impermissibly interferes with rightsholders’ ability to effectuate their constitutional interests.