The benefits of green roofs have finally been recognized in the UK by release of Living Roofs and Walls: Technical Report to Support the London Plan. This has lead lead to the first direct policy in the deliver green roofs in the UK, and probably one of the strongest outside of continental Europe.
The policy states:
'The Mayor will and the boroughs should expect major developments to incorporate living roofs and walls wherever feasible and reflect this in LDF policies.'
Worldwide Green Roof Policy - Regional Statements
Toronto initiates a green roof policy and implementation programme.
See page 20 of the .pdf
Toronto Policy Statement [.pdf 400KB]
an overview of portland oregon's green roof policy.
Portland Green Roof Policy [.pdf 200 KB]