CYIL 7 ȍ2016Ȏ INTERNATIONAL ADMINISTRATIVE LAW AND ADMINISTRATIVE ACTS… have become interested in transboundary effects of administrative decision making since the 1990s. In describing their subject of interest some of them prefer the term “transnational” decision making ( Angelos Gerontas, 25 Giacinto Della Cananea, 26 Marie Gautier 27 ), while other scholars use the term „extraterritorial“ decision making ( Hervé Ascensio, 28 Stefano Battini, 29 Lydia Lebon 30 ). Most recently, both terms have become the subject of criticism due to their relative ambiguity. Therefore, the term “transterritorial” administrative decision making is preferred by other authors ( Hertwig Hofman 31 ). This term will be used also in this article. 4. In the 4 th volume of his monumental study on “International Administrative Law” the visionary Karl Neumeyer pointed out three prospective features of transboundary (transterritorial) administrative decision making: (1) administrative decision making by international administrative unions (vertical transterritorial decision making), (2) transterritorial decision making of national administrative authorities (horizontal transterritorial decision making) and (3) administrative decision making of national administrative authorities as result of coordinated transterritorial proceedings. At the time that Karl Neumeyer identified these three prospective features of transterritorial decision making, he could provide only a very few practical examples for each of them. However, taking the restored interest in “international administrative law” into consideration, this article will point out current challenges arising from these features. 1. 5. Delegating of administrative powers to international organisations (international administrative unions) represents a phenomenon which has attracted the attention of the science of administrative law since the era of the “belle epoque” . A number of contemporary authors reflected the establishment of a number of these unions ( European Commission of the Danube in 1856, International Telegraph Union in 1865, 26 DELLA CANANEA, G . Transnational public law in Europe : beyond the lex alius loci , in: Maduro, M., Tuori, K., Sankari, S. (ed.) Transnational Law , Cambridge University Press, Cambridge, 2014, pp. 321 et seq. 27 GAUTIER, M. Acte administratif transnational et droit communautaire , in: Auby, J., Dutheil de la Rochere, J. (eds.) Droit administratif européen , Ed. Bruylant, Bruxelles, 2007, pp. 1069 et seq . 28 ASCENSIO, H. Extraterritoriality as an instrument , Sorbonne Law School, University of Paris 1, 2010, pp. 27 et seq . 29 BATTINI, S. Extraterritoriality : an Unexceptional Exception , in: Zwart, G., Auby, J., Morison, J. (eds.) Values in Global Administrative Law , Hart Publishing, Oxford, 2011, pp. 65 et seq . 30 LEBON, L. La territorialité et ľ Union européenne. Approches de droit public , Ed. Bruylant, Bruxelles, 2015, pp. 45 et seq . 31 HOFMANN, H. Dealing with Trans-Territorial Executive Rule Making , Missouri Law Review, 2013, pp. 424 et seq. 25 GERONTAS, A. Deterritorialization in Administrative Law: Exploring Transnational Administrative Decisions , Columbia Journal of European Law, 2013, pp. 423 et seq.