What is the country of origin? Please point out to me where the Aztec country is. Do you mean Mexico? Are they entitled to all the relics of the past civilizations theirs crushed? And yes, I know the idol in Indiana Jones isn’t really Aztec, but the overall point stands.
With the exception of the very few cases where a country can actually trace its culture and history all the way back to when those artifacts were made, ancient culture and artifacts belong to humanity as a whole, not whatever geopolitical entity happens to control the land they’re on at the time of discovery. It’s not a natural resource, it’s human history.
Would it be ok if Spain took it then?