This research project aims to analyse what in doctrine has been called the Achilles heel of ICSID arbitrations, i.e. the obstacle posed by the theory of State immunity to the enforcement of arbitration awards rendered against sovereign States by arbitral tribunals constituted under the provisions of the Washington Convention of 1965, establishing, under the auspices of the World Bank, the International Centre for the Settlement of Investment Disputes (ICSID). This research project aims to analyse the various solutions that have been proposed by the doctrine and practice to the problem of enforcement of ICSID awards and to propose a solution that will be a balance between the prerogatives of the State and the investor's rights. In the discussion several cases, even non ICSID ones, will be examined as their analysis is essential in order to illustrate common issues and draw common solutions. It is structured as follows: after a brief reconstruction of the regulatory framework, we will analyse the problems related to immunity from execution of the State in the context of the ICSID arbitral awards and finally we will address the different means of enforcing awards proposed and possible approaches to the issue.