++++ 1. EEC Treaty ° Single European Act ° Expiry of the period fixed for the establishment of the internal market ° Effects ° Obligation of Member States to amend conditions of affiliation to their social security scheme ° None in the absence of legislation from the Council (EEC Treaty, Art. 8a) 2. Social security for migrant workers ° Voluntary or optional continued insurance ° Admission subject to condition of prior affiliation to the national scheme ° Obligation of a Member State to admit to affiliation to its scheme a person insured only under the legislation of another Member State ° None ° Affiliation allowed for nationals who previously worked in a non-member country ° No effect (Council Regulation No 1408/71, Art. 9(2))