This paper deals with the connection between law and morality. Such a connection is relevant for political theory, since demonstrating that law necessarily implies a claim to justice would require fundamental rights to be considered the horizon of any legal system, instead of being considered as dependent on the axiological context of liberal democracies. The paper approaches the controversy starting from an overview of the work of the German philosopher Robert Alexy, in particular his attempt to establish an analytical link between law and morality, and to this end considers law as a speech act with a claim to correctness. It then examines the critique put forward by Joseph Raz, that points out the lack of objectivity of this claim to correctness. In order to establish a moral foundation for law, the paper argues that it is necessary to take account of Karl-Otto Apel's attempt to establish the transcendental foundation of language, as well as of Habermas' critique of that attempt. In conclusion, it is argued that the debate about a possible link between law and morality sheds new light on contemporary debates on liberal justification in political theory.