This provision is one of a number dealing with the relations between the Scottish Parliament and Executive and the European Union.  Schedule 5 provides that international relations including those with the European Communities (and their institutions) are to be reserved to the UK Parliament and Government.  But the Scottish Parliament and Executive are responsible for observing and implementing obligations under Community law in relation to devolved matters.
Section 29 provides that it is ultra vires for the Scottish Parliament to legislate in a way that is incompatible with Community law.  Section 53 transfers to the Scottish Ministers any functions of Ministers of the Crown of observing and implementing Community Law in relation to devolved matters in or as regards Scotland.  Section 57(1) provides that, notwithstanding that transfer, Ministers of the Crown shall continue to be able to exercise those functions as regards Scotland for the purposes specified in section 2(2) of the European Communities Act 1972.  Section 57(2) provides that it is ultra vires for the Scottish Executive to make subordinate legislation or otherwise to act in any way which is incompatible with Community law.
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