R (ClientEarth No.2) v Secretary of State for Environment, Food & Rural Affairs, Garnham J, 2 November 2016, judgment here
This is all about nitrogen dioxide in air, an unwanted byproduct of the internal combustion engine. Its effect on UK mortality has been estimated at 23,500 deaths per year.
The short version is this.
The UK has been non-compliant with EU Directive 2008/50 on nitrogen dioxide (et al) over the last 6 years. Art.23 of the Directive requires that the period in which a state is obliged to remedy any non-compliance is to be “as short as possible”.
The UK Air Quality Plan (AQP) produced in 2015 (and responding to the 2nd Supreme Court judgment here) was simply not up to ensuring that urgently required result.
In so concluding, Garnham J started with the construction of Art.23, in response to a Defra argument that it imports an element of discretion and judgment.