Facts
A. AG, a construction company in X. (municipality of Saas-Balen), stored large quantities of mineral construction waste at the site. Following information from the Department for Environmental Protection, the Cantonal Building Commission of the Canton of Valais (KBK) ordered an immediate suspension of work on 11 September 2013.
By decision of 5 December 2013, the KBK ordered A. AG, B. and C. to restore the lawful state on parcels nos. a, b, c, d (sheet no. x, locality 'Y.'). The container structure was to be completely demolished, inert materials and excavated material disposed of in an environmentally sound manner, building materials and containers removed, the terrain restored in accordance with the natural course, the vegetation cover renewed, and the parcels returned to their original agricultural use.
The Council of State of the Canton of Valais dismissed the appeal against this decision on 21 February 2018. The Cantonal Court of Valais confirmed the decision on 23 November 2018.
A. AG as well as B. and C. filed a public law appeal with the Federal Supreme Court and requested that the decision be set aside or, alternatively, remitted. They relied on a building permit dated 18 September 1967, subsequently discovered by the municipality, of which they had first become aware on 31 December 2018. The Federal Office for the Environment (BAFU) commented on the environmental law aspects. The watercourse area of the Saaser Vispa had been established by the municipality on 2 April 2017 and approved by the Council of State on 20 June 2018.
The dispute concerned in particular whether Art. 41c para. 2 WPO, in the case of non-conforming buildings outside the building zone, establishes an independent guarantee of acquired rights, or whether the protection of acquired rights is governed by Art. 24c SPA, and whether the reconstruction of the building under the former law can be authorised retrospectively.
Considerations
Existing structures in the watercourse area are, pursuant to Art. 41c para. 2 WPO, in principle protected in their existence, provided they were lawfully erected and can be used as intended. It is disputed whether this provision has independent significance for non-conforming buildings outside the building zone, or whether the protection of acquired rights is governed by Art. 24c SPA and by the balancing of interests under Art. 24c para. 5 SPA and Art. 43a lit. e SPO.
In judgment 1C_345/2014, the Federal Supreme Court departed from its earlier view and holds that Art. 41c para. 2 WPO contains a guarantee of acquired rights that is independent of Art. 24c SPA. The wording protects only 'the existence' and mentions neither alteration, extension nor reconstruction, to which Art. 24c para. 2 SPA refers. Art. 24c SPA, moreover, permits only exceptions to zone conformity, whereas buildings in the watercourse area are unlawful under water protection law regardless of zone conformity.
Systematically, the heightened protection of the watercourse area argues against an extended protection of acquired rights. Pursuant to Art. 41c para. 1 WPO, location-dependence alone is not sufficient; the installations must depend on their location in the watercourse area and be in the public interest. This serves the natural functions of watercourses and flood protection (Art. 36a para. 1 WPA, Water Construction Act), the protection of riparian areas as habitat (Art. 18 para. 1bis NCHA), and later revitalisation (Art. 38a WPA). That the protection of acquired rights is…