There's been plenty of discussion as to the similarities between the Cons' terror bill and Pierre Trudeau's 1970 invocation of the War Measures Act. And it's certainly worth reminding ourselves that even in the face of an identifiable security concern, the impulse to attack civil rights tends to prove wrong upon reflection.
But there's a key difference between the C-51 debate and Trudeau's invocation of the War Measures Act - and it's one which makes the present-day Cons and Libs look even worse than their predecessors.
Keep in mind that the War Measures Act was aimed at providing extreme but temporary powers in the face of an apprehended threat. Those powers still exist under a statute which replaced the War Measures Act, which provides barely-fettered authority under a few key conditions: the government is required to publicly declare a state of emergency, its declaration is temporary unless extended, and its decision is subject to the will of Parliament.
In contrast, the key parts of the security apparatus set up under C-51 lack some or all of those protections.
C-51's warrant process provides for the actions which require judicial approval to be time-limited in theory. But just as the granting of a warrant takes place away from the public eye and without opposition, so too does the extension of a warrant.
What's worse, the no-warrant provisions of C-51 operate any time CSIS decides for itself - without any debate or notice - that a "particular activity" should be limited. Once that standard is met, CSIS is authorized to take whatever actions it sees as reasonable, with no limit on the time or scope of any intrusion into the lives of Canadians other than CSIS' own evaluation.
And there's no process for anybody to challenge or review CSIS' secret actions - which again can be carried out indefinitely - except to the extent SIRC is up to the task.
In retrospect, history has proven Tommy Douglas right in arguing that the 1970 application of the War Measures Act resulted in the Trudeau government using a sledgehammer to crack a single peanut. But by that standard, the Cons' C-51 is based on implementing the vision of a sledgehammer being used to smash a pile of peanuts forever.
[Edit: fixed wording.]