You might want to do some research on elf/alf. They almost always leave a calling card. They want everyone to know when they pull these stunts. And I would not bet on anyone getting caught. These nut jobs are very smart and they have learned a lot for Al-Qaeda. They have loose knit cells and practice very good operational security.
I just did some browsing and I have to say you're right.
The level of eco-terror being what it is, seems like it's high time mere membership in ELF is enough to consign their asses to a Gitmo type prison for ever.
Maybe a nice place like the Meadowlands where they can appreciate the beauty of development.
Well, they generally don't leave a calling card at destructive acts of terrorism.
And, they only take credit when it appears that nobody died, so as not to admit to homicide.
Such upstanding people.