Ioana Tudor, supra note 1; Gabriel Cavazos Villanueva, The Fair and Equitable Treatment Standard: The Mexican Experience (VDM Verlag 2008); Roland Kläger, Fair and Equitable Treatment in International Investment Law (CUP 2011); Alexandra Diehl, The Core Standard of International Investment Protection: Fair and Equitable Treatment (Wolters Kluwer 2012); Martins Paparinskis, The International Minimum Standard and Fair and Equitable Treatment (OUP 2013); Todd Weiler, The Interpretation of International Investment Law: Equality, Discrimination and Minimum Standards of Treatment in Historical Context (Martinus Nijhoff 2013).

 Dumberry, supra note 4, pp. 44–46.

 As mentioned above, supra note 1, out of 365 BITs examined by the present author, 197 FET clauses examined contain some additional specifications that this treatment prohibits arbitrary and/or discriminatory measures. Also, while a number of BITs (65) contain an ‘unqualified’ stand-alone FET clause, others make explicit reference to international law (70) or to customary international law (5).

 Dumberry, supra note 4, pp. 127–274.

 Stone, supra note 12, p. 94, referring to a number of cases.

 Hamrock, supra note 12, pp. 849–863, referring to a “nebulous test” and proposing instead its own four-stage test.

 Stone, supra note 12, p. 94, referring to a number of cases.

 Newcombe and Paradell, supra note 24, pp. 250–251; Todd Weiler and Ian Laird, ‘Standards of Treatment’ in P. Muchlinski, F. Ortino and C. Schreuer (eds.), The Oxford Handbook of International Investment Law (OUP 2008) 284–285 (“international law prohibits state officials from exercising their authority in an abusive, arbitrary, or discriminatory manner. The tell-tale sign of the kind of state conduct which attracts such liability is an apparently arbitrary, capricious, and/or overtly discriminatory governmental action which causes damage to a foreign investment. If state officials can demonstrate that the decision was actually made in an objective and rational (i.e. reasoned) manner, they will defeat any claim made under this standard. If they cannot, the arbitrary conduct must be remedied”).

 Heiskanen, supra note 12, pp. 111, 104. The same test is put forward by Diehl, supra note 2, p. 453. Hamrock, supra note 12, pp. 852 et seq., proposes another test.

 Diehl, supra note 2, pp. 448 et seq.; Restatement of the Law Third: The Foreign Relations Law of the United States, para. 712, note 11 (American Law Institute Publ. 1987).

 Heiskanen, supra note 12, p. 104 (“The distinction between arbitrary and unreasonable governmental conduct boils down to this: a governmental measure can be considered ‘arbitrary’ if no justification or rationale at all has been provided for the measure (i.e. if there is no relationship at all, let alone a rational relationship, between the measure and a legitimate governmental policy); and it can be considered ‘unreasonable’ if a justification or a rationale has in fact been provided for the measure, but there is no reasonable (or rational) relationship between the purported justification and a legitimate governmental policy”).

 Newcombe and Paradell, supra note 24, p. 304. See, however, Benedict Kingsbury and Stephan Schill, Investor-State Arbitration as Governance: Fair and Equitable Treatment, Proportionality and the Emerging Global Administrative Law 11–12 (New York Univ. Public Law & Legal Theory Research Paper Series Working Paper No. 09–46) 10, 16, identifying “reasonableness and proportionality” as one of the “five clusters of normative principles” which “recur in the more detailed specification by arbitral tribunals of elements of fair and equitable treatment”.

 Tyler, supra note 36, pp. 50, 68–69, referring to a number of cases.

 Newcombe and Paradell, supra note 24, pp. 237, 249–250; Christoph Schreuer and Rudolf Dolzer, Principles of International Investment Law (OUP 2008) 176; Todd Weiler, ‘Methanex Corp. v. U.S.A: Turning the Page on NAFTA Chapter Eleven?’ (2005) 6 J. World Invest. & Trade 917; Weiler and Laird, supra note 27, pp. 284–285. Contra: Heiskanen, supra note 12, p. 110 (for whom “non-impairment standard [prohibiting arbitrary and unreasonable acts] imposes a standard of conduct on governments that is arguably substantially higher than that required by customary international law”); Paparinskis, supra note 2, p. 239; Santiago Montt, State Liability in Investment Treaty Arbitration (Hart Publ. 2009) 295, 310.

 Schreuer, supra note 28, p. 5; Diehl, supra note 2, p. 448; Katia Yannaca-Small, ‘Fair and Equitable Treatment Standard: Recent Developments’ in A. Reinisch (ed.), Standards of Investment Protection (OUP 2008) 121.

 Stone, supra note 12, p. 95 (referring to a number of non-NAFTA cases).

 Schreuer, supra note 28, p. 6, referring to a number of cases.

 Schreuer and Dolzer, supra note 146, pp. 173–174; Stone, supra note 12, pp. 90–91; Newcombe and Paradell, supra note 24, p. 299.

 Schreuer, supra note 28, pp. 5 et seq.

 Schreuer, supra note 28, p. 5 (referring to a number of cases).

 Stone, supra note 12, p. 91; Vasciannie, supra note 22, p. 133; Heiskanen, supra note 12, p. 94.

 Schreuer, supra note 28, p. 7; Schreuer and Dolzer, supra note 146, p. 175; Diehl, supra note 2, p. 449.

 Tudor, supra note 1, p. 180 (“when it is found that a measure has clearly been arbitrary and discriminatory, the breach of the FET obligation is almost a natural conclusion”).

 Diehl, supra note 2, p. 452, see also at p. 450 (“a breach of the non-impairment standard will always be a breach of the FET standard, while the absence of discrimination will not have any impact on the findings concerning the breach of FET”).

 Stone, supra note 12, p. 103 (“Where the two regimes begin to diverge is the level of arbitrariness that could lead to a successful claim. While both regimes typically use high thresholds (ELSI), [non-NAFTA] arbitral tribunals have been willing to entertain lower thresholds for finding arbitrariness than their NAFTA counterparts”). Stone explains (at 97) that the following measures have been found to be (or not to be) in violation of the prohibition of arbitrariness outside of NAFTA: “Government measures that have been found to be arbitrary include threats and the blocking of payments to a foreign-owned water treatment company, the transfer of contractual rights of a foreign-owned media company to one that was domestically owned [Lauder] administrative decisions causing investor confusion regarding a country’s tax regime [Occidental], a breach of contract and eventual privatization of a state-owned hotel that had contracted with a foreign investor [Alpha], and the permanent suspension of a foreign investor’s operations after substantial investment [Siemens]. Conversely, instances in which claims of arbitrariness were found wanting involved measures that were deemed arbitrary but did not substantially impair the investment [CMS] that had been the subject of negotiations with the investor [LG&E]; that were consistent with pre-investment measures, if not more onerous [AES]; that were justified by a period of economic transition in an emerging economy [Genin]; and that were made in response to an economic crisis [Enron, Sempra]”.