Membership agreements signed by member states
Includes 4 freedoms - free movement of goods, capital, services, labour
Directly applicable to citizens
Have direct effect on all citizens -vertical direct effect & horizontal direct effect
Founding - set up EU ---> Treaty of Rome 1957
Accession - when new members join ---> Treaty of Accession 1972
Amending - when changes are made ---> Treaty of European Union 1992