The Environmental Defense Fund, founded in 1967 in New York, is a very large and active global environmental not for profit group that current has 700,000 members. Since the 1960s and moving forward the EDF has taken on various green campaigns including legislation against the use of chemicals like DDT, clean air and water acts, pollution reduction, and global warming initiatives. The EDF probably would not be considered by most an extremist environmental group and even according their own site they “believe economic prosperity and environmental stewardship go hand in hand.”  They tend to seek collaborative, “market-based” solutions to environmental issues and even have corporate partnerships with companies like FedEx and McDonalds.
However, looking at the items below, the language like “taking offenders to court” is a much more confrontational than what you see on their website now. It seems like the EDF must have gradually moved away from some of its more radical/militant approaches and rhetoric. The EDF is one of many groups in the collection that probably would not be considered very extreme now, but at the time it was collected would be categorized by Gordon Hall as “dissenting” or “groups that were not yet extremist, but might at some point turn in that direction.”