This article analyses how the fair and equitable standard is applied by international tribunals from the interpretation of the clauses of the bilateral investment treaties, establishing a tension with the notion of regulation, as States police power on the economic activities within their territories. We try to show how international tribunals deal with this tension defining limits to the States powers and fixing the scope to the standard. This article is the first part of the study mentioned above, and the second section will address the Arbitration Court’s judicial decisions within the North American Free Trade Agreement.