If a just and well-ordered political community is integral to the good for an individual, then it would seem incumbent on the architectonic legislator and prudent statesperson to aim at the optimal condition of the polis and hence to reform defective regimes and laws. The normative structure of Aristotle’s constitutional theory – with its conception of the best regime as an ideal and appeal to the common advantage as a central criterion for distinguishing correct and defective constitutions – likewise suggests a progressive stance towards correction of political injustice. The overall attitude towards the reform of constitutions and laws which emerges from the Nicomachean Ethics and Politics is nonetheless cautious and conservative. In the current chapter I consider the motivations for this circumspection and argue that it reflects both the importance of habituation to the effective functioning of law and a recognition of the limits of law’s capacity to promote virtue and human flourishing. Section 1 engages in a close reading of Aristotle’s treatment of the advantages and disadvantages of legal reform in the Politics Book II.8 discussion of Hippodamus’ legislative proposal to honour innovation. In section 2, I examine Aristotle’s account of constitutional change and stability in light of his theory of ethical virtue. Finally, in section 3, I turn to political obedience and argue for its dual justification within Aristotle’s practical thought.