[1] A Belgian law required margarine to be marketed in cube shaped packages, to avoid confusion with butter.

Walter Rau argued that the law contravened (what is now) TFEU article 34.

It cannot be reasonably denied that in principle legislation designed to prevent butter and margarine from being confused in the mind of the consumer is justified.

However, the application by one member state to margarine lawfully manufactured and marketed in another member state of legislation which prescribes for that product a specific kind of packaging such as the cubic form to the exclusion of any other form of packaging considerably exceeds the requirements of the object in view.

Consumers may in fact be protected just as effectively by other measures, for example by rules on labelling, which hinder the free movement of goods less.