The general situation is that if land currently used as a public park is to be used for development, then the development plan would have to be varied accordingly. The usual procedures, involving public consultation etc., in relation to the variation of a plan would have to be followed. Any rezoning could also be made in reviewing a development plan.
Whether such a change of zoning would be sufficient in itself to procure such a change of use depends on the particular circumstances of the public park in question. If the park was governed by particular statutory provisions it may require legislation. If the land was gifted to a local authority for use as a public park, it is possible that the use of the land for other purposes would be restricted by the terms of the gift. However, if the land was acquired by compulsory purchase for use as a public park, then it is possible that the local authority could designate the land for another use.
Local authorities have general powers, under the Local Government Act, 1994, to provide, operate and maintain parks and open spaces for amenity and recreational purposes but no specific procedures are laid down for this purpose.