(1) Law amending the constitution and other constitutional acts are adopted by each of the two chambers twice within no less than three months and need the approval of a majority of the members of each chamber in the second voting.
(2) Such laws are afterwards submitted to popular referendum when, within three months of their publication, a request is made by one fifth of the members of either chamber, by 500,000 electors, or by five regional councils. The law submitted to referendum is not promulgated if it does not receive the majority of valid votes.
(3) No referendum may be held if the law has been approved by each chamber in the second vote with a majority of two thirds of its members.
