Canada’s Communications Security Establishment commissioner, Antonio Lamer, has been asking tough questions recently of the agency about trespassing in Canadian communications.

Correspondence obtained by the Canadian Press shows that recent revelations in the United States over National Security Agency spying on domestic communications prompted a series of highly-classified exchanges in Ottawa between Lamer, CSE’s official watchdog, and CSE chief John Adams. Over a span of two months, Lamer’s office grilled the agency about the extent of CSE eavesdropping on Canadians.

Until the passage of Canada’s Anti-Terrorism Act in 2001, the very existence of CSE was cloaked in secrecy. Since the 1940s, the spy agency has been involved almost exclusively with foreign intelligence activities, trolling through the phone calls and later the emails, faxes and Blackberry messages of foreign countries for foreign intelligence beneficial to Canadian interests.

Along with NSA in the U.S. and counterpart agencies in Britain, Australia and New Zealand, CSE participated in a worldwide surveillance network known as Echelon, but under Canadian law CSE was forbidden to data mine on Canadian soil.

The 2001 legislation changed the ground rules. Mirroring the secret and arguably illegal NSA no-warrant spying program authorized by U.S. President George W. Bush, the act explicitly allows CSE to spy within Canada’s borders. That has Lamer worried CSE’s eavesdropping powers might extend to the same massive trolling inside Canada that it ordinarily performs internationally within its original mandate, and that NSA and the Bush Administration are under fire for in the U.S.

The Canadian public will know more when the commissioner’s annual report to Parliament is released later this year.