The Executive and the External Affairs Power: Does the Executive's Prerogative Power to Vary Treaty Obligations Qualify Parliamentary Supremacy?

The Commonwealth Parliament is conferred legislative competence to implement treaty obligations by the external affairs power. What is the status of implementing legislation if the executive subsequently exercises its power to vary Australia’s treaty obligations, and where that legislation cannot otherwise be constitutionally supported? This comment argues that the external affairs power should be understood as waxing and waning analogously to the defence power. The result is that the executive may undermine the validity of implementing legislation by varying treaty obligations. However, the sense of unease engendered by this conclusion may, to some extent, be mitigated by implying a legislative intention that implementing legislation should not endure beyond the facts that support its validity.