@clacke And the cross religion marriage in Indonesia currently can't be administered legally.
https://www.hukumonline.com/klinik/a/nikah-beda-agama-cl290/
Apparently, cross religion marriage was allowed, but in some conditions, including if one of them are ignoring the religion norm. But now, seems the chance of it has been closed. As from government perspective, cross religion marriage may also invalid from the religion perspective too.
If religion perspective invalid = invalid by legal law too.