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The tribunal has stated that the amici curiae approached the issues ‘with interests, expertise and perspectives that have been demonstrated to materially differ from those of the two contending parties, and as such have provided a useful contribution to these proceedings.’ 123 The tribunal ultimately decided that Tanzania has breached its obligations, but did not order the state to pay damages, as the damage the investor has allegedly sustained was not contributable to Tanzania. 124 The need to comply with human rights obligation did not excuse the breach of BIT obligations committed by the state. However, it helped to break the chain that linked this breach to the damaged that was caused. 125 The tribunal did not refer to amicus curie submission in the final part of its analysis and it did not in any way hint that it reached its conclusions solely based on the submission. However, given that the tribunal repeatedly pronounced the submission ‘useful’, 126 it may be assumed that the submission contributed to the outcome of the case. Biwater v Tanzania therefore confirms that as discussed in section V.A, non-party actors may contribute to the proceedings by bringing new arguments to the table and by better explaining arguments that were already put forward. D. Amicus Curiae as the Key to Promoting Human Rights in International Investment Arbitration? Previous sections revealed several important pieces necessary for answering the question whether amicus curiae can help to promote human rights in international investment arbitration. Firstly, the global level of protection of human rights is threatened only in those instances where states attempt to use them in their defensive arguments. Secondly, states have mostly failed in these cases in the past for one of two reasons: either they attempted to invoke the state of necessity, which can be successful only under very strict conditions (and although they could have, 127 BITs did not ease those conditions); or states are unwilling or unable develop the argument. Thirdly, amicus curiae may introduce new arguments and perspectives to the proceedings and it may also increase transparency and ignite a public debate on the topic. A combination of these elements leads to the conclusion that amicus curiae can under certain factual circumstances indeed help to promote human rights in international investment arbitration. If the states are unable or unwilling to pursue the argument, amicus curiae can help them. Biwater v Tanzania shows that amicus curiae is capable of bringing a meaningful contribution to the case and introduce additional arguments. Instead of arguing the state of necessity, as Argentina did in other cases, amicus curiae

123 ibid [359]. 124 ibid [805]. 125 cf Marella (n 39) 358.

126 Biwater v Tanzania (n 44) [359], [392]. 127 Cf Sempra v Argentina (n 38) [375] in fine .

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