How is national government related to same-sex marriage?

Answer 1

In some countries, such as France and Spain, the national government has total control over marriage laws for the entire country. In cases like that, same-sex marriage can be legalized all at once for the entire country.

In other countries, such as the United States, Canada, Mexico and Brazil, each individual state has their own marriage laws. In such cases, same-sex marriage can be legalized state-by-state, or the federal courts can issue a decision forcing all states to legalize same-sex marriage. In Canada, a federal law was passed legalizing same-sex marriage in all provinces. In Mexico, a supreme court decision forced all states to recognize same-sex marriages, but did not force them to perform them. In Brazil, the supreme court ruled that same-sex couples are entitled to be married and some states permit same-sex marriages, but others have refused and same-sex couples must be married by court order on a case-by-case basis. In the United States, the federal government has prohibited itself from recognizing same-sex marriages and permitted states to do the same, while also allowing states to legalize it if they so choose.

In the case of the United Kingdom, the Westminster parliament has delegated control over marriage laws to separate parliaments in Scotland and Northern Ireland, while maintaining control over England and Wales. Parliament is currently considering legalizing same-sex marriage in England and Wales. Its power is supreme in Scotland and Northern Ireland, but that power has been delegated to local parliaments in those member nations, which will decide for themselves whether to legalize same-sex marriage.