Evidence-based practices and comparative effectiveness research are salient topics in public policy. Empirical validation of agency operating processes provides agencies and policy-makers the opportunity to address uncertainty surrounding effectiveness. While this is an increasingly accepted rational approach to public policy, the exact mechanism for how this operates is less known. In order to evaluate several theoretical assumptions and normative rational expectations inherent in this approach, the implementation of a state legislative mandate stating policy expectations for behavioral health evidence-based practices is assessed. This study sought to assess whether implementation patterns and associated outcomes reflect "rational mechanism" policy expectations. While the premise of this research surrounds a state behavioral health legal mandate, results inform broader health policy efforts. Study results identify some evidence that the policy yielded "rational mechanism" processes and outcomes, but also indicated that other mechanisms may have influenced implementation patterns. In addition, evidence of a link between policy and outcomes is at best inconsistent. Further research on evidence-based policies using definitional and measurement frameworks applied in this study is clearly warranted.