Obviously the server will be able to delete those rows because it will be completely unaware of this dependency.
So it is the implied reverse constraint (of sorts) that can't be enforced which makes an FK based definition impossible.
For my particular use case, this shouldn't be a problem. The foreign table is a reference table which does not typically experience deletes. I'll go with a function for now. Since this happens to be a PostgreSQL-PostgreSQL mapping I'll also consider mapping my table back the other way and then putting a delete trigger on the foreign reference table to either cascade or stop the delete once I decide which I'd rather do.
Thanks for the help!
