Not by law and the will of the people, but dictatorial judicial fiat.
Same-sex marriage was enacted by popular vote in MD, ME and WA. A referendum to ban same-sex marriage was defeated in MN.
Same-sex marriage was enacted by the vote of the legislatures in CT, DC, DE, HI, IL, MN, NY, RI and VT.
Same-sex marriage was also enacted by the state legislatures in CA and MA after prior bans had been struck down by the courts.