Final answer:
The Defense of Marriage Act (DOMA) prevented same-sex marriages from being recognized in other states.
Step-by-step explanation:
The legal act that was prevented from being recognized in other states by DOMA (Defense of Marriage Act) was same-sex marriage. DOMA, which was passed in 1996, explicitly limited the definition of marriage to a union between one man and one woman and allowed individual states to choose whether or not they recognized same-sex marriages performed in other states. This meant that even if a same-sex marriage was legally recognized in one state, it might not be recognized in another state due to DOMA.