Agricultural lands acquired or held in violation of sections 1¹ and 4² shall be forfeited to the Commonwealth. The Attorney General shall enforce such forfeiture. However, no such forfeiture may be adjudged unless the action to enforce is brought within five years after such property has been acquired or held by such alien. No title to land is invalid or liable to forfeiture by reason of the alienage of any former owner or person interested therein.