Radical constructivists appeal to self-legislation in arguing that rationalagents are the ultimate sources of normative authority over themselves. I chartthe roots of radical constructivism and argue that its two leading Kantianproponents are unable to defend an account of self-legislation as the fundamentalsource of practical normativity without this legislation collapsing into a fatalarbitrariness. Christine Korsgaard cannot adequately justify the critical resourceswhich agents use to navigate their practical identities. This leaves her accountriven between rigorism and voluntarism, such that it will not escape a paradoxthat arises when self-legislation is unable to appeal to external normativestandards. Onora O’Neill anchors self-legislation more ﬁrmly to the self-disciplining structures of reason itself. However, she ultimately fails to defendsufficiently unconditional practical norms which could guide legislation. Theseendemic problems with radical constructivist models of self-legislation prompt areconstruction of a neglected realist self-legislative tradition which is exempliﬁedby Christian Wolff. In outlining a rationalist and realist account of self-legislation,I argue that it can also make sense of our ability to overcome anomie anddeference in practical action. Thus, I claim that we need not make laws but canmake them our own.