As aforementioned, one of the most important contemporary trends in the transformation of judicial review of legislation, particularly in concentrated systems, has been the development of the possibility for constitutional courts to exercise their power to control the constitutionality of statutes, interpreting them according to the Constitution without being obliged to decide on the nullity of the unconstitutional provisions.
The same sort of control is also exercised regarding the constitutionality of the conduct of the Legislator, not related to statutes duly enacted, but regarding the absence of such statutes or the omissions the statutes contain when the Legislator does not comply with its constitutional obligation to legislate on specific matters or when the Legislator has passed legislation it in an incomplete or discriminatory way. It is important to highlight in all these cases that judicial review decisions adopted by constitutional courts are issued completely separate from the need to annul existing statues, as it is impossible in these cases to characterize the constitutional courts as negative legislators. On the contrary, in many of these cases, constitutional courts act openly as positive legislators, often with the possibility to issue declarations of unconstitutionality of certain legal provisions without annulling them. In some ways, this is similar to what occurs in diffuse systems of judicial review, where the courts have no power at all to annul statutes.
Two sorts of legislative omissions can generally be distinguished: absolute and relative omissions.