In this essay the Kantian thesis of the pacific character of republic is examined, including the question of how the Kantian intuition of the connection between form of government and peace has been developed by contemporary philosophers, since Michael Doyle’s essay entitled «Kant, liberal legacies and foreign affairs». Kant’s explicit argument to explain the pacific character of republic is a non-moral one; it is a strategic one. The first part of the paper is dedicated to showing that it is possible to find implicit moral arguments. Four of them are identified them (related to the idea of republic): 1. The normative idea of law, 2. Government per leges, 3. The democratic form of government and, finally, 4. The Principle of publicity. Each of those specific elements of the idea of republic has a relationship of morality that can explain the pacific character of this constitution. In the second part of the essay it is argued that the Kantian heritage on this theme shouldn’t be related (only) to the pacific character of the democratic form of government, but (also) to the democratic constitution paradigm. Indeed, considering also the Kantian implicit arguments, we can update it considering them similar to the argument of two contemporary philosophers: Norberto Bobbio and Jürgen Habermas. They connect the «elements» of the democratic constitution paradigm —the rights, the separation of powers and the democratic form of government— to peace, as well as all the «elements» of the idea of republic (not only the democratic one) is connected to the peace. We can consider that as an «updating» of the Kantian thought because the elements of the democratic constitution paradigm, at least those ones elaborated by Norberto Bobbio e Jürgen Habermas, can be considered a development of the elements of the Kantian idea of republic.