I posed the question in title in an earlier post on this blog. In an article published in the current issue of the International Journal of Constitutional Law, Liav Orgad provides one possible answer. Here is the abstract:
From Plato’s Laws through common law and until modern legal systems, preambles to constitutions have played an important role in law and policy making. Through a qualitative analysis of the legal status of preambles in different common law and civil law countries, the article highlights a recent trend in comparative constitutional law: the growing use of preambles in constitutional adjudication and constitutional design. The article also explores the theory of preambles and their functions. It examines the legal status of the U.S. preamble and shows how the U.S. preamble remains the most neglected section in American constitutional theory. The article then presents a typology for determining the legal status of preambles: a symbolic preamble, an interpretive preamble, and a substantive preamble. While focusing on Macedonia, Israel, Australia, and the Treaty of Lisbon, the article discusses the sociological function of preambles in top-down and bottom-up constitutional designs.
An earlier version is available on SSRN. It’s a fascinating piece, as applicable to the preamble to the Irish Constitution as it is to those discussed by Orgad. As he notes, “courts have been invoking the Preamble in order to interpret the Irish Constitution and as a guiding tool to understand its spirit and values”. Indeed, there is a long tradition of making use of the preamble in the interpretation of the provisions of the Constitution, from McGee v AG  IESC 2,  IR 284 (19 December 1973) and Norris v AG  IESC 3,  IR 36 (22 April 1983) through McGimpsey v Ireland  IESC 3,  IR 567 (1 March 1990), AG v X  IESC 1,  1 IR 1 (5 March 1992) and In re Article 26 and the Regulation of Information (Services outside the State for the Termination of Pregnancies) Bill 1995  IESC 9,  1 IR 1 (12 May 1995) to Laurentiu v Minister for Justice  IESC 47,  4 IR 26 (20 May 1999) and A v The Governor of Arbour Hill Prison  IESC 45,  4 IR 88 (10 July 2006).