Since this headline seems to be getting far more attention than the actual accompanying interview (if mostly from people with a strong vested interest in distorting the NDP's position), let's take a moment to discuss what we'd expect a responsible party to do upon taking power - and what we can tell from a party's actions while in opposition.
The NDP has rightly taken the position that C-51 deserves to be defeated. And it's thus making a strong push to challenge the bill both in premise and in its details - in stark contrast to the Libs, who have pledged their unconditional support despite the fact they recognize serious flaws.
That doesn't mean the NDP shouldn't work to try to reduce the damage as the bill is dealt with in Parliament - including by offering amendments along the way.
But we know that the Cons will be able to force the bill through, particularly since the Libs won't actually be opposing it even if the Cons refuse amendments to try to improve it. So what then should the NDP should do upon taking power?
One option would be to treat C-51 with the same single-word level of analysis we know so well from the U.S. Republicans. And it's certainly tempting to treat the worst of Stephen Harper's choices as deserving nothing more than a declaration of "repeal!".
In the meantime, though, it's entirely likely that some national security practices will have changed based on the passage of C-51. And pulling the rug out from under those practices without assessing the consequences would be just as irresponsible as the Cons' habit of forcing through changes without proper thought.
Meanwhile, we'll also have new information in the meantime about how CSIS has actually used its new powers, and what steps might be most appropriate to rein them in. And it makes no sense to demand that any party close its eyes to that information.
Finally, let's note that the parties' actions now should send a strong signal as to their intentions upon forming government. The Libs' position is that they're more accepting of C-51 than concerned with it, and if they made any amendments at all after the fact we'd expect relatively little change. Conversely, the NDP sees C-51 as doing more harm than good such as to justify voting it down now - offering ample reason to believe it would be highly skeptical of Harper's changes in deciding what amendments are required later.
In sum, there's no immediate damage to current security operations in opposing
the creation of new powers, where there could be in eliminating them
after they exist. And while we should hold Tom Mulcair to the standard
of deleting any parts of C-51 (and any other security legislation)
which aren't justified as soon as can be done without disrupting our
security services, that doesn't mean a "scrap it all immediately!" position is in anybody's interest.