Our local gendarmes have bicycles, and they do patrol our trails.

Perhaps a word to the local chief or sheriff would assist in getting this dangerous pace-line practice stopped. Also, perhaps a couple of more directive signs along the trail,

"No Pace Lines"

"Trail Not to be used for Training"

would assist.

A letter to the editor?

A local TV spotlight on the problem?

Do you have a local advocacy group in the state or city?

Our state advocacy group has been very effective in situations like this.

http://bicyclecolo.org/index.cfm

And we have had TV coverage and spotlight of dangerous situations.

Good on you for your EXCELLENT method of handling this on the spot. Did you report the incident to the local police? I mention this because don't be too surprised if the rider you were restraining DOES report it, along with a claim of injury from your restraint.

Incidentally, this squirrel thing is one more reason for wearing a helmet, even on trails.