Part X Constitutional Amendment

Section 166

The right to propose a constitutional amendment shall be exercised under the provisions of section 87, subsections 1 and 2.

Section 167

1. Bills on constitutional amendments must be approved by a majority of three-fifths of members of each House. If there is no agreement between the Houses, an effort to reach it shall be made by setting up a Joint Committee of an equal number of Members of Congress and Senators which shall submit a text to be voted on by the Congress and the Senate.
2. If approval is not obtained by means of the procedure outlined in the foregoing subsection, and provided that the text has been passed by the overall majority of the members of the Senate, the Congress may pass the amendment by a two-thirds vote in favour.
3. Once the amendment has been passed by the Cortes Generales, it shall be submitted to ratification by referendum, if so requested by one tenth of the members of either House within fifteen days after its passage.

Section 168

1. If a total revision of the Constitution is proposed, or a partial revision thereof, affecting the Introductory Part, Chapter II, Division 1 of Part I, or Part II, the principle of the proposed reform shall be approved by a two-thirds majority of the members of each House, and the Cortes Generales shall immediately be dissolved.
2. The Houses elected thereupon must ratify the decision and proceed to examine the new constitutional text, which must be passed by a two-thirds majority of the members of each House.
3. Once the amendment has been passed by the Cortes Generales, it shall be submitted to ratification by referendum.

Section 169

The process of constitutional amendment may not be initiated in time of war or under any of the states contemplated in section 116.