An Answer to Pier Paolo Portinaro - Answering the questions posed by the discussants on the occasion of the Turin presentation of his Principia iuris, Ferrajoli goes back to the relationship between politics and law, on the separation of powers, and on legislative power. The global constitutionalism paradigm is put forward not as a utopia, but as the only realistic proposal - in the long run - to avoid a future of war, violence and terrorism. Crucial, within this paradigm, is the separation between the institutions of government and the institutions of guarantee: the first are made legitimate by political representation, the latter by their being subordinate to law only. With respect to legislative power, Ferrajoli clarifies that if, from one point of view, it is free to make discretionary choices in the « sphere of what needs to be decided », respecting the constitution, on the other point of view, it is obliged to introduce guarantees to protect rights in the « sphere of what cannot be decided ».