Laws are adopted by the National Assembly and the Senate, and promulgated by the King or the acting Head of State. Laws must be in strict conformity with the Constitution.
A Royal Decree is issued by the King in the exercise of his constitutional powers. A Royal decree must be in strict conformity with the Constitution.
Sub-Decrees are adopted by the Council of Ministers and signed by the Prime Minister. Sub-decrees must be in strict conformity with the Constitution and conform to the Law to which it refers.
A Prokas is a ministerial or inter-ministerial decision signed by the relevant Minister(s). A proclamation must conform to the Constitution and to the law or Sub-Decree to which it refers.
A Circular is an instrument that a Ministry or higher authority use to clarify a point of law or to provide instructions. A circular is only advisory and does not have the force of law.