This article argues that even if states ought to defer to the Supreme Court concerning the meaning of cognate constitutional provisions, such deference is not required in considering the reach of prophylactic rules. Such rules, while constitutional in status, are not vessels of constitutional meaning. Rather, they are a pragmatic means to implement more open-ended constitutional norms and thus, by design, are adjustable where necessary to improve their fitness for that task. The Supreme Court makes such adjustments, and there is no reason why states should not also be able to do so where local conditions suggest the need for a more protective rule. A state’s expansion of a prophylactic rule leaves untouched the meaning of the underlying federal principle, along with the Supreme Court’s prerogative to decide what that meaning is. This article analyzes such rule expansions under Massachusetts law to develop this point concretely. . .
