A crucial turning point for the establishment of ELDO was the legal settying up of its machinery. The Preparatory Group organised n.5 Sub-groups devoted to the study of the legal context of the future ELDO, namely the Contracts Sub-group, the Security Sub-group, that dealing with the transmission of information and with the contractual provisions
moreover the Rules of Procedure and the Immunities Sub-groups, studying the situations in member and non-member states
finally, the Patents Sub-group, in order to protect the intellectual property rights.