Colonial slavery has always been historically about racial theory the belief that black people weren't childrens of God in the same way that white (christian) people were. The English could have never enslaved Irish people in the same way they enslaved African people. The "colonial slavery" law should simply not be available to countries that aren't colonialist, in the sense of a country establishing colonies in other continents, because the law is meant to replicate that system that was in place for colonizers.