NANOG makes a fine archive of discoverable material in a court case intending to show collusion to drive folks out of business.
One presumes that each ISP here has some form of AUP and rules on self-preservation roughly along the lines of "if there is material impact to my network or my customers, I can do whatever it takes to mitigate the traffic/intrusion". One does not need to collaberate with others before enforcing your own AUP. --bill