OBJECTIVES: There is a perception that the National Institute of Health and Care Excellence (NICE) has struggled to get clinical commissioning groups (CCGs) to follow guidelines. There is a legal obligation to follow NICE technology appraisal guidance (TAG) when these are accompanied by a funding direction; however it has long been considered that this was not the case for Clinical Guidelines (CGs) nor is there any right of appeal in relation to CGs. We seek to demonstrate that CGs could be effectively mandatory unless a reasoned justification is provided. The position is contrasted with respect to guidance from technology appraisals. METHODS: Case law and legislation are reviewed to compare the enforceability of general guidelines and health technology appraisal-derived guidance. In particular Regina vs. North Derbyshire Health Authority, ex parte Fisher (1997) (Regina), and the recent decision of Rose vs. Thanet CCG (Rose) are referred toWe review both the CGs and TAGs issued and compare the strength and range of the recommendations. RESULTS: The Reginacase established that a decision not to follow national policy was only lawful if there was some ‘special factor’, which ‘exceptionally justified departure’. Disagreement with the policy was not enough. Following this, the recent Rose case considered that the CCG was under an implied obligation to give reasons for any general policy not to fund a particular intervention, which suggests that the guidance is effectively mandatory unless there are special grounds. CONCLUSIONS: Even if the Rose decision were successfully appealed or distinguishable, CCGs will need to consider special circumstances if they do not wish to implement a CG. Along with financial constraints on health budgets, this creates dilemmas for CCGs including local priority setting. Therefore, as the law stands, exceptional circumstances will need to be identified by CCGs taking a contrary decision to a CG.