National uniform legislation exists in federations to implement national reforms where the central government does not have the direct authority to legislate under the Constitution. The State jurisdictions must work together on legislation to address urgent issues of national concern, national uniform legislation. Developing and drafting national uniform legislation are complicated and complex because they require the cooperation of many units with asymmetrical knowledge, competing priorities, limited budgets and timeframes, and at times irreconcilable differences. Empirical data analysis and statistics could provide an aid for decision-making in these circumstances. On examination of a large body of legal information on the 69 most significant Australian national reforms, this article finds factors that inhibit or promote sustainable uniformity of enacted legislation by using ordinal regression for the first time. This work provides significant evidence-based insights into the process of harmonisation in federations. Overall, our findings contradict the general belief that the uniformity is mostly dependent on structures alone (referred, applied, mirror, and hybrid). If sustainable uniformity is the goal,the decision-makers must allow resources for establishing the national regulator, ensure maximum uptake by the majority of the nine Australian jurisdictions, support the development of national uniform legislation through the National Cabinet, and be prepared for the second wave of national reforms through consecutive reforms. These findings have valuable strategic implications for policymakers, law reform agencies, and legislative drafters who intend to rely on evidence for future decision-making in terms of the most important national reforms. This paper provides recommendations for governments intending to ensure the sustainability of uniformity and adaptability of the Australian legislation for any future changes without losing the important consensus that has been achieved. The findings are also important for other federations seeking to implement harmonised legislation.