Surely that presupposes that one of the parties is not Filipino (dual Nationality). Thus that course must be followed. But here we have two Filipinos getting married in RP. I can't see that dual nationally affects that.
In this case I would ask, is the marriage recorded at NSO ? If it is then it is a valid marriage. If it is not, then why can't it be registered ?
Perhaps Puppylov can answer this, as without that knowledge, I think we are likely to go off at tangents.