From the letter:
Second, we believe that Bill C-51 will effectively grant the Communications Security Establishment (CSE), which is empowered to assist CSIS, an implicit offensive mandate to act within Canada. There is little sober second thought in the new open-ended world of covert action that C-51 creates for CSE. New CSE digital disruption activities can include measures such as the false attribution of disreputable content to individuals, and even planting of malware on individual computing devices.
We are already concerned about the negative impact the activities of CSE and CSIS, including reports of spying on our trading partners, have had on Canada’s reputation. The impact of these new rules could collapse the necessary distance between investigative and executional powers. This distance should be increased, not done away with.
Read it all on National Post.