While any migration of an invasive species generally situates the species in its new region permanently until something kills it off (and as such you must conti

While any migration of an invasive species generally situates the species in its new region permanently until something kills it off (and as such you must continually guard against invasive species entering), we would only have to prevent re-migrations of the "tainted" species back to their native regions for the amount of time that it would take them to die out due to the sterilization. Much easier. Edit: relaxed claims.