Levelling environmental standards would undermine regional diversity and opportunities for testing new environmental solutions.
Harmonized standards may be weaker than other standards and may have no legal authority under which they can be effectively enforced. They are often only guidelines which governments may, or may not, enforce. The best way to harmonize law is to write it and enforce it at the highest level. The best way to promote disharmonization is to hand the responsibility over to a committee of diverse parties.