PULP MILLS (JUDGMENT) 60 nificant transboundary harm to another State must be notified by the party concerned to the other party, through CARU, pursuant to Article 7, second and third paragraphs, of the 1975 Statute. This notification is intended to enable the notified party to participate in the process of ensuring that the assessment is complete, so that it can then consider the plan and its effects with a full knowledge of the facts (Article 8 of the 1975 Statute). 120. The Court observes that this notification must take place before the State concerned decides on the environmental viability of the plan, taking due account of the environmental impact assessment submitted to it. 121. In the present case, the Court observes that the notification to Argentina of the environmental impact assessments for the CMB (ENCE) and Orion (Botnia) mills did not take place through CARU, and that Uruguay only transmitted those assessments to Argentina after having issued the initial environmental authorizations for the two mills in question. Thus in the case of CMB (ENCE), the matter was notified to Argentina on 27 October and 7 November 2003, whereas the initial environmental authorization had already been issued on 9 October 2003. In the case of Orion (Botnia), the file was transmitted to Argentina between August 2005 and January 2006, whereas the initial environmental authorization had been granted on 14 February 2005. Uruguay ought not, prior to notification, to have issued the initial environmental authorizations and the authorizations for construction on the basis of the environmental impact assessments submitted to DINAMA. Indeed by doing so, Uruguay gave priority to its own legislation over its procedural obligations under the 1975 Statute and disregarded the well-established customary rule reflected in Article 27 of the Vienna Convention on the Law of Treaties, according to which “[a] party may not invoke the provisions of its internal law as justification for its failure to perform a treaty”. 122. The Court concludes from the above that Uruguay failed to comply with its obligation to notify the plans to Argentina through CARU under Article 7, second and third paragraphs, of the 1975 Statute. C. Whether the Parties Agreed to Derogate from the Procedural Obligations Set Out in the 1975 Statute 123. Having thus examined the procedural obligations laid down by the 1975 Statute, the Court now turns to the question of whether the Parties agreed, by mutual consent, to derogate from them, as alleged by Uruguay. 124. In this respect the Parties refer to two “agreements” reached on 2 March 2004 and 5 May 2005 ; however, they hold divergent views regarding their scope and content. 50