It's a dirty war and I've a nasty, decidedly unfair and mean spirited idea. Inject the released ones with rabies. It's hard to spread to others (although who cares), invariably fatal and easy to blame on the animals in the area creating plausible denial.
Sounds good to me! I can keep a secret.
Surreptitiously implant a GPS tracking chip before release. When they go to rejoin their Taliban/Al Qaida pals in Pakistan or Tora Bora ... deliver a GBU-28 welcoming gift onto the whole gang.