The Constitutional Court decides about the harmonization of the law with the Constitution, with generally accepted rules of international law, and with ratified international treaties.   
State institutions (for example, President of the Republic, a Ministry, etc.), institutions of territorial autonomy (for example, the Assembly of the autonomous province), or local self-government bodies (for example, Municipal Assemblies), a minimum of twenty five MPs, and the Constitutional Court itself can initiate proceedings before the Constitutional Court.
On the other hand, any legal (for example, a company) or physical entity (individual person) has the right to initiate proceedings for the assessment of constitutionality and legality.