Federations often have special procedures for amendment of the federal constitution. As well as reflecting the federal structure of the state this may guarantee that the self-governing status of the component states cannot be abolished without their consent. An amendment to the constitution of the United States must be ratified by three-quarters of either the state legislatures, or of constitutional conventions specially elected in each of the states, before it can come into effect. In referendums to amend the constitutions of Australia and Switzerland it is required that a proposal be endorsed not just by an overall majority of the electorate in the nation as a whole, but also by separate majorities in each of a majority of the states or cantons. In Australia, this latter requirement is known as a double majority.
What does federations have for amendments of the constitution? 
special procedures