This PhD thesis in Spatial Planning argues for the importance of understanding the approaches to knowledge and rationalities embedded in spatially relevant decision-making. It emphasises the significance of seeing law as an empirical object of study for planning and environmental management. The Swedish development of wind power and 3G mobile infrastructures are used as cases to study these issues of principal interest. It is a compilation thesis consisting of a comprehensive introductory framework and five articles or chapters that have also been published elsewhere. The study is based on three main perspectives: Level of decision-making, legitimacy of different forms of knowledge involved in the process, and the sociolegal tension between formal law and its practical consequences. The thesis deals with problems stemming from the multi-level tensions in the planning and implementation that exist between the national, the regional and the local authorities. The legal context is analysed from the sociolegal perspective, in particular how the juridification of siting and permit conflicts determines what type of knowledge that can legitimately affect the decision-making and thereby set conditions for public participation. Finally, the thesis elaborates on the largely counterproductive results of the strong emphasis on “efficiency” in the revision of planning and permit processes for wind power and 3G-infrastructure, and what can be learnt from the experiences of the attempts at increasing efficiency. A combination of methods has been employed in the studies, and the data comes from a range of sources such as a large set of mast building permits, a sample of wind permit cases, as well as appealed permit cases. In addition, interviews have been conducted with judges from relevant courts, including regional handling officers who assess wind turbine applications. Legal documents such as preparatory work and licence conditions have also been analysed. The results show that there is a legal-rhetorical adaptation to the expert-based decision-making in court when permits are appealed. Further, the administrative levels interact poorly in the overall implementation. The national decisions, irrespective of the normative viewpoint of who should control the landscape planning, could be better informed of the preconditions at a local level that factually define the outcome of the implementation. The author, Stefan Larsson, holds a PhD in Sociology of Law, an LLM and is a sociolegal researcher who generally studies issues in the intersection of conceptual, sociolegal and technological change. The thesis has been supervised by Professor Lars Emmelin, The Swedish School of Planning, BTH, and co-supervised by Professor Karsten Åström, the Department of Sociology of Law, Lund University. The thesis is the result of research within the programme Tools for environmental assessment in strategic decision-making, MiSt, funded by The Swedish Environmental Protection Agency and the Centre for Work, Technology and Social Change at Lund University.