In 2006, a prohibition on less favourable treatment of workers related to parental leave was introduced in The Swedish Act on Parental Leave. The prohibition was designed on the basis of the rules on discrimination of pregnant workers and workers on maternity leave in the Equal Treatment directive. The Swedish rules do however separate from the EU rules in one crucial respect. While the European Union law principally does not allow any exception from the prohibition on discrimination on the grounds of pregnancy and maternity leave, the Swedish Parental Leave Act in some cases allows an employer to treat a worker less favourable on the ground of parental leave. Such less favourable treatment is allowed in cases where the less favourable treatment can be seen as a necessary consequence of the parental leave or the maternity leave. The overall aim for this article is to discuss different problems that may be a result of the method of legislation used for the Swedish rules on protection of workers related to parental leave. On one hand, these national rules are intended to be in principle fully equivalent to the corresponding EU rules on pregnancy and maternity leave. But on the other hand, the national provisions are provided with an exception that has no parallel in the European Union law. As the national rules only partly is in coherence with the union law, the legal argumentation concerning these rules can only partly refer to principles of European Union law and to jurisprudence from the Court of Justice of the European Union. A difficulty related to this method of legislation is thus to make clear to what extent guidance as to interpretation of the national law can be found in EU law. Another problem connected with this method of legislation is that it may cause the national law to diverge from the EU law in a way that is not legally acceptable. Regarding the Swedish Parental Leave Act this problem have been discussed in relation to the level of protection granted for employees on maternity leave, as these employees are covered both by the strict rules on protection provided in EU law and by the less strict provisions in the Swedish Parental Leave Act.