This is because I agree that determining whether a statute is unconstitutional, and decisions of limited constitutionality and limited unconstitutionality, are also a kind of decision of unconstitutionality and are the Constitutional Court's own power. Of course, questions may arise in that the Supreme Court made possible the kind of limited-constitutionality or limited-unconstitutionality interpretation described above, but I think the conclusion of the judgment under review is sound in terms of harmonizing tax law with the Constitution, interpreting Articles 6 and 13 of the addenda to the amended act harmoniously, and protecting the predictability of applying tax law and taxpayers' legal stability.

For reference, Article 18(2) of the Framework Act on National Taxes provides that income, profits, property, acts or transactions for which the obligation to pay national tax has been established shall not be taxed retroactively under new tax laws enacted after that establishment. Its roots are the prohibition in Article 13(2) of the Constitution on deprivation of property rights by retroactive legislation and the principle of no taxation without law in Article 59. The case number 2013Du23185 written in the material appears to be a typo for the actual judgment 2013Du23195, so when citing it in an assignment be sure to check the number and date of judgment at the National Law Information Center. It is even better to read it against the original text of the summary of the judgment.