German legislation, which provided for notice periods to be calculated according to length of service but did not take into account any service below the age of 25, discriminated on the grounds of age.

The ECJ found that the legislation had the legitimate aim of affording employers greater flexibility and alleviating the burden in respect of the dismissal of younger workers for whom it was reasonable to expect a greater degree of personal and occupational mobility. However it could not be justified, as it was not a proportionate way of achieving that aim. It applied to all employees who were 25 when they began their employment regardless of their age or length of service at the time of their dismissal. Thus employees with the same length of service could be less favourably treated solely on the grounds of their age at the time of joining.

The ECJ went on to hold that a national court faced with domestic legislation that it considers to be incompatible with a general principle of EU law (such as the principle of non-discrimination on the grounds of age) must decline to apply the offending provision, even in a case involving proceedings between individuals and there was no need to refer the matter to the ECJ before doing so (Kücükdeveci v Swedex GmbH & Co).