In Portugal and Spain, reserva is a regulated term controlled by law, at least ensuring that reserve wines get some additional ageing. In practice it is very difficult to regulate quality, so the term primarily deals with ageing and alcoholic strength. In Portuguese and Spanish wines, the requirements varies between regions, but typically, when used on a label "Reserva" means that the wine was aged for at least three years in the cask and bottle, at least one of which must have been in the cask.