Chapter 1 • International Human Rights Law and the Role of the Legal Professions: A General Introduction there is, as a minimum, an ethical duty under international law for corporations to run their businesses in such a manner as to respect basic human rights.52 States may have an international legal obligation to ensure adequate protection in their domestic law against human rights violations committed by business corporations. Business corporations may themselves have legal obligations in the field of human rights derived from domestic law. At the international level business corporations are considered to have, as a minimum, an ethical responsibility to respect fundamental human rights. 4. International Human Rights Law at the Domestic Level 4.1 Incorporating international law into domestic legal systems As previously noted, and as provided in article 27 of the Vienna Convention on the Law of Treaties, a State “may not invoke the provisions of its internal law as justification for its failure to perform a treaty”. On the other hand, States are free to choose their own modalities for effectively implementing their international legal obligations, and for bringing national law into compliance with these obligations. Since domestic legal systems differ considerably in this respect, albeit also having some similarities, it will be for each domestic judge, prosecutor and lawyer concerned to keep himself or herself informed as to the manner of incorporation of the State’s international legal obligations into national law. Below, a mere general account will be given of the various ways in which a State can modify its municipal law so as to bring it into conformity with its international legal obligations. v First, according to the monist theory, of which there are in fact several divergent versions,53 international law and domestic law can in general terms be described as forming one legal system. This means that once a State has ratified a treaty for the protection of the human person, for instance, the terms of that treaty automatically become binding rules of domestic law. 52 Suggested reading on the question of business corporations and human rights: Michael Addo, Human Rights Standards and the Responsibility of Transnational Corporations (The Hague, Kluwer Law International, 1999); and Alan Dignam and David Allen, Company Law and the Human Rights Act 1998 (London, Butterworth, 2000). 53 See Ian Brownlie, Principles of Public International Law (Oxford, Clarendon Press, 3rd edn., 1979), p. 34. 20 Human Rights in the Administration of Justice: A Manual on Human Rights for Judges, Prosecutors and Lawyers