The principle of denial of justice embodies the maladministration of justice by local courts. Prohibited acts of the local judiciary mainly revolve around access to justice, discrimination and the slow or non-existent execution of court decisions which are favorable to a foreign investor.
One of the oldest and most oft-cited definitions of denial of justice is the definition found in the L. Fay, H. Neer and Pauline Neer (USA) v. United Mexican States case. As defined by the tribunal in Neer:
[T]he treatment of an alien, in order to constitute an international delinquency, should amount to an outrage, to bad faith, to willful neglect of duty, or to an insufficiency of governmental action so far short of international standards that every reasonable and impartial man would readily recognize its insufficiency.
The content of the principle of denial of justice can be found in the Ambatielos case. There, the tribunal stated that:
[T]he foreigner shall enjoy full freedom to appear before the courts for the protection or defence of his rights, whether as plaintiff or defendant; to bring any action provided or authorised by law, to deliver any pleading by way of defence, set off or counterclaim, to engage Counsel, to adduce evidence, whether documentary or oral or of any other kind; to apply for bail, to lodge appeals and, in short, to use the Courts fully and to avail himself of any procedural remedies or guarantees provided by the law of the land in order that justice may be administered on a footing of equality with nationals of the country.(emphases added)
A more recent definition of denial of justice comes from the Azinian v. Mexico arbitration, which identified four types of denial of justice:
A denial of justice could be pleaded if the relevant courts refuse to entertain a suit, if they subject it to undue delay, or if they administer justice in a seriously inadequate way… There is a fourth type of denial of justice, namely the clear and malicious misapplication of the law. (emphases added)
A broader definition of denial of justice was found in the Loewen v. USA arbitration. There, the arbitral tribunal concluded that a denial of justice required a “manifest injustice in the sense of a lack of due process leading to an outcome which offends a sense of judicial propriety”. Although the tribunal in Loewen ultimately ruled that it lacked jurisdiction, it concluded that proceedings before an American court were so biased that they amounted to a denial of justice.
Denial of justice may concern criminal proceedings. The tribunal in Tokios Tokelés highlighted violations of basic principles of conduct in criminal proceedings as a manifestation of denial of justice.
Denial of justice may also concern local administrative proceedings. This was notably the case in the Metalclad v. Mexico case, where Mexican administrative authorities wrongfully failed to issue a permit to a foreign investor.
 L. Fay, H. Neer and Pauline Neer (USA) v. United Mexican States, RIAA, Volume IV pp. 60-66, 15 October 1926, p. 60.
 The Ambatielos Claim (Greece v. United Kingdom of Great Britain and Northern Ireland), RIAA, Volume XII pp. 83-153, 6 March 1956.
 The Ambatielos Claim (Greece v. United Kingdom of Great Britain and Northern Ireland), RIAA, Volume XII pp. 83-153, 6 March 1956, p. 111.
 Robert Azinian, Kenneth Davitian, & Ellen Baca v. The United Mexican States, ICSID Case No. ARB (AF)/97/2, Award (1 November 1999), paras. 102,103.
 Loewen Group, Inc. and Raymond L. Loewen v. United States of America, ICSID Case No. ARB(AF)/98/3, Award (26 June 2003), para. 132.
 Grand River Enterprises Six Nations, Ltd., et al. v. United States of America, UNCITRAL, Award (12 January 2011), para. 223.
 A. de Nanteuil, Droit International de l’Investissement, Editions A. Pedone, 2014, pp. 324-325.
 Tokios Tokelés v. Ukraine, ICSID Case No. ARB/02/18, Award (26 July 2007), para. 133.
 Metalclad Corporation v. The United Mexican States, ICSID Case No. ARB(AF)/97/1, Award (30 August 2000).
 Robert Azinian, Kenneth Davitian, & Ellen Baca v. The United Mexican States, ICSID Case No. ARB (AF)/97/2, Award (1 November 1999), para. 99.