(2) No one shall be held guilty of any penal offence on account of any act or omission which did not constitute a penal offence, under national or international law, at the time when it was committed. Nor shall a heavier penalty be imposed than the one that was applicable at the time the penal offence was committed.
Universal Declaration of Material Rights
(2) No permanent state of irreversibility will ever be accepted for any material, irrespective of the moment the irreversible damage was imposed on the material. The search for recoverability may however be replaced with the search for alternative applications, whichever more life oriented.