Final answer:
The U.S. Supreme Court's United States v. Windsor opinion addressed the issue of same-sex marriage, ruling that a section of DOMA was unconstitutional and that the federal government must recognize same-sex marriages for federal benefits.
Step-by-step explanation:
The U.S. Supreme Court's decision in United States v. Windsor was a landmark case that addressed issues pertaining to same-sex marriage. The Supreme Court ruled that a section of the Defense of Marriage Act (DOMA), which denied federal recognition of same-sex marriages, was unconstitutional under the Fifth Amendment. This decision in 2013 paved the way for the federal government to recognize same-sex marriages across the United States and provided equal federal benefits and protections to married same-sex couples.
The Windsor ruling also set the stage for a cascade of federal court decisions that overturned state bans on same-sex marriage, significantly increasing the number of states that permitted it. Following these developments, in 2015, the Supreme Court case Obergefell v. Hodges extended the right to marry to same-sex couples nationwide based on the Fourteenth Amendment.