The Polish legal system belongs to the system of codified law. There is an element besides legislation and case-law that brings additional knowledge about Poland's regulatory framework regarding the expropriation of real property – the legal doctrine developed within the academic aspect of law. The main legislative act regulating expropriation of real property in Poland is the Land and Property Management Law, henceforth UGN. Expropriation through UGN takes or limits rights in rem — full ownership, land usufruct and lesser rights. The ordinary legislation has not given the expropriation beneficiary freedom to identify what is a public purpose instead, it has provided a catalogue of enumerated public purposes in terms of functions, activities and facilities. If the subject property experiences value growth or a decrease as a result of activities undertaken by the beneficiary directly after the expropriation, the indexed compensation amount is adjusted to incorporate these value changes as at the return date.