Planning Policy Wales
Relevant policies include the following:

5.3.6   National Parks and AONBs are of equal status in terms of landscape and scenic beauty and both must be afforded the highest status of protection from inappropriate developments. In development plan policies and development management decisions National Parks and AONBs must be treated as of equivalent status. In National Parks and AONBs, development plan policies and development management decisions should give great weight to conserving and enhancing the natural beauty, wildlife and cultural heritage of these areas.

5.3.11  Non-statutory designations, such as Special Landscape Areas or Sites of Interest for Nature Conservation, should be soundly based on a formal scientific assessment of the nature conservation, landscape or geological value of the site. Local non-statutory sites can add value to the planning process particularly if such designations are informed by community participation and reflect community values. Local planning authorities should apply these designations to areas of substantive conservation value where there is good reason to believe that normal planning policies cannot provide the necessary protection. Such designations should not unduly restrict acceptable development.

5.5.6  In National Parks or AONBs, special considerations apply to major development proposals which are more national than local in character. Major developments should not take place in National Parks or AONBs except in exceptional circumstances. This may arise where, after rigorous examination, there is demonstrated to be an overriding public need and refusal would be severely detrimental to the local economy and there is no potential for locating the development elsewhere or meeting the need in some other way.

5.7.2  Development plans should normally only propose coastal locations for development which needs to be on the coast. In particular, the undeveloped coast will rarely be the most appropriate location for development. Where new development requires a coastal location the developed coast will normally provide the best option, provided that due regard is paid to the risks of erosion, flooding or land instability.

5.7.4 Policies should aim to protect or enhance the character and landscape of the undeveloped coastline. Planning policies to be pursued in Heritage Coast areas should be incorporated in development plans. Designation as a heritage coast does not directly affect the status of the area in planning terms. However, the features which contributed to the designation of such areas may be important in formulating planning polices or making development management decisions.

6.5.24 World Heritage Sites are a material consideration to be taken into account by local planning authorities in the determination of planning applications, and by the Welsh Government in determining cases on appeal or following call-in. The impact of development proposals on both the sites and their settings should be carefully considered.

6.5.25 Local planning authorities should protect parks and gardens and their settings included in the first part of the ‘Register of Landscapes, Parks and Gardens of Special Historic Interest in Wales’. Cadw should be consulted on planning applications affecting grade 1 and II* sites and the Garden History Society should be consulted on all parks and gardens on the Register. Information on the historic landscapes in the second part of the Register should be taken into account by local planning authorities in considering the implications of developments which are of such a scale that they would have a more than local impact on an area on the Register (see para 6.4.9). The effect of proposed development on a park or garden contained in the Register of Landscapes, Parks and Gardens of Special Historic Interest in Wales, or on the setting of such a park or garden, may be a material consideration in the determination of a planning application.