Lawmaking is a challenging exercise: prospective in nature, highly controversial and only partly rational. Its main challenge is having to anticipate that legislative solutions have the capacity to work. In this context, effectiveness, as the capacity of legislation to do the work it is intended to do, provides a concrete decision making criterion for the choices involved in lawmaking. Effectiveness can play this role because (contrary to efficacy and efficiency that look at other functions of legislation) it reflects the ‘mechanics’ of the legislative text and depicts its capacity to function as a system. Its content reflects the systemic coherence and alignment between four fundamental elements of legislation: objectives, content, context and results. From this perspective effective legislation is the result of complex mechanics in the conceptualisation, design and drafting of the law and cannot materialise unless it is a clear concern in the early phases of lawmaking.