All awards are one-way. It is possible to cancel and reinstate miles for one way, but it would have to be all segments of that one-way award. You would then have to claim a new award, and make a new reservation, to replace those segments if you still needed to travel in that direction (either the return or the outbound). It *should* be possible to keep the other segments (separate award, for the other direction of travel) intact. Just call AA and ask.

also, for international itineraries (for those who might look at this thread in the future), keep in mind that some countries won’t let you clear immigration as a visitor unless you have a round-trip itinerary, or other proof that you will be departing the country.