According to article 12 TEU “national parliaments contribute actively to the good functioning of the Union”. To fulfill this duty national parliaments have several powers at their disposal. The first type of powers are those laid down in EU law itself. The EU Treaties thus provide every parliament of an EU member state with the right to review draft legislation of the EU for its compatibility with the subsidiarity principle (Early Warning System), to start a political dialogue with the European Commission as well as the possibility to take part in interparliamentary cooperation.

In addition to the powers given to national parliaments at EU level, national parliaments have also been vested with powers at national level to participate in EU affairs, even though such powers can vary from one member state to another. Examples of this type of power include the existence of a scrutiny reserves or the right to ask questions to the government. In her research, Sofie looks at how the Dutch and German parliaments make use of their powers to participate in EU affairs in practice, both at EU and at national level, and identifies the factors determining the level of activity of the two parliaments when it comes to EU affairs.