That you can be sure of, and I don’t know whose “Slavic” tradition this is, but it sure as hell is not Polish tradition.

Polish father and non-Polish mother produces child that is half-Polish and half-whatever else and is considered so in Poland. I am sure it is same in Russia (hence designations for “Rossiyanin” and “Rusak” in Russia to separate natives from foreigners, just like for example in France you have “Francais” and “Gallois”) and I can’t imagine it being different in other Slavic countries, including Serbia.

If your father is Polish and your mother Belorussian, you are considered Polish I believe. Because you are the continuation of the Polish lineage not a Belorussian one. Such is the tradition among all Slavic people of south-eastern Europe and I believe among all Slavs. You may have different roots but one lineage.

If your mother is not a Slav, especially not of the same race, I doubt you’ll be accepted by others as a Slav. Traditionally people didn’t have anyone else but their Slavic compatriots to marry, only today in the modern times this is different.

Sibiryak, I do not support foreign immigration less than Slavic one or of compatible acceptable cultures, to some extent. I would never allow Albanians to migrate to our lands, but since they are already here it is better to integrate them, than to chase them out with guns, and make them hostile towards us… because as we all saw it, it didn’t work out too good. Not with the muhajirs (Bosniaks, Albanians etc.) nor with any other minority. In other words it is daydreaming.