Parliament exercises most of its powers in the area of Catalonia but also participates in the activity of central institutions of the State.

Parliament is responsible for appointing the senators who are to represent the Generalitat in the Senate, set up by the Constitution as the House that represents the nationalities and regions that make up the State.

The Parliament of Catalonia has the right to propose legislation before the Spanish Congress: it can present a bill leading to a law. The Statute also recognizes the right of the Parliament to request the State Government to adopt a bill whose processing corresponds to the Spanish Parliament. Both procedures allow the Parliament to contribute to the creation of a legislative system beyond what is strictly Catalan in scope.

With respect to powers not included in the Statute - on which, in principle, the Generalitat cannot act - the Parliament may ask the State to transfer or delegate them to the Generalitat. Moreover, the State has exclusive authority over a series of areas provided by the Constitution, but the Parliament of Catalonia can ask the Spanish Parliament to give it the authority in these areas to dictate laws that develop the legal framework of the State.

The Constitution is the most important legal framework of the State and cannot be contravened by other laws. The role of the Constitutional Court is to guarantee its correct application and interpretation, and laws dictated by the Spanish Parliament or by the legislative assemblies of the autonomous communities can be contested before this body.

If the Parliament feels that a law of the State invades the area of autonomy of Catalonia, it can ask the Constitutional Court to annul the law contrary to the Constitution or to the Statute, by lodging an appeal for unconstitutionality.

The State of the autonomies configured by the Constitution includes the distribution of powers among the central institutions of the State and those of the autonomous communities. Should a conflict of authority arise between the Government of the State and the Generalitat, or between the latter and another autonomous community, it falls to the Constitutional Court to rule on a solution to the conflict. The Parliament of Catalonia can appear before this Court to state its opinion or can require the Government to do so.