Chapter III elucidates the application of attribution rules by international investment tribunals. This chapter is similar in structure to Chapter II, which is a consequence of the proximity of international investment law to public international law with regard to the topic of attribution of conduct to a party. In addition, this chapter contains critical discussion on investor–State dispute settlement (ISDS), chiefly on the dialectics between lex generalis (customary international law) and lex specialis (international investment law) as to the resolution of attribution issues, and on the distinction between treaty claims and contract claims for the purposes of the operation of so-called ‘umbrella clauses’. More generally, the chapter critiques the reasoning of arbitrators who have applied the test for attribution of conduct under ARSIWA Articles 4, 5, and 8 in a holistic way, rather than implementing each single test autonomously.