Yes. So long as the marriage license is filed for, completed, and returned Stateside, the marriage will be legal. With the legal obligations taken care of, you and the couple are free to conduct the ceremonial part of the wedding anywhere you wish.
If the couple wishes to have the marriage legally recorded outside the United States, it can lead to complications. Many countries will not allow non-citizens to file for marriage licenses and the minister authorization process may be difficult, if not impossible. Not all countries provide equal rights to all churches and ministers, and becoming an officiant in another country can be a complicated, time consuming process.
If the marriage absolutely must legally occur outside the United States, and you aren’t able to register as a minister-officiant, you may be able to complete a temporary civil-officiant registration. Finally, remember that if you perform a marriage outside of the United States, you must follow the marriage laws of the country where you perform the ceremony.