1.25. Moreover, the development of disposal facilities that incorporate provisions in design or operation to facilitate reversibility, including retrievability, is considered in several national programmes for waste management. In some States, post-closure retrievability is a legal requirement and constitutes a boundary condition on the options available, which must always satisfy the safety requirements for disposal. No relaxation of safety standards or requirements could be allowed on the grounds that waste retrieval may be possible or may be facilitated by a particular provision. It would have to be ensured that any such provision would not have an unacceptable adverse effect on safety or on the performance of the disposal system. This subject is not extensively dealt with in this Safety Requirements publication.