Why is the European Commission called the guardian of the treaties?

The European Commission is referred to as the "guardian of the treaties" because of its fundamental responsibility to represent the interests of the European Union as a whole, rather than the individual interests of its member states.1

This role is rooted in the Commission's mandate to enforce the treaties and legislation that serve as the legal foundation for the EU and its communities. By ensuring that these laws are upheld and administered consistently, the Commission acts as a protector of the legal framework that binds the member states together. To maintain impartiality, commissioners are required to act independently and are strictly forbidden from taking instructions from their respective national governments.1