As far as section 7 of the Charter is concerned, you cannot be deprived of your liberty, unless it is in line with the principles of fundamental justice. But what certain provisions of the bill say is more or less that you will be jailed for an indeterminate period of time, except if you will never be a threat in the future. So the onus is on the person to prove that something will never happen in the future. Of course, that is a fairly bizarre burden of proof.
Section 7 was at issue in the 1987 Supreme Court ruling in the Lyons case. In this ruling, the reason why the process was upheld was because the burden of proving that someone was a dangerous offender fell to the Crown, which had to prove this beyond a reasonable doubt. This was a key point in the Lyons decision at the time.
The Supreme Court even ruled that the fact that the Crown was not obliged to give notice that it would call for a dangerous offender hearing did not violate the Charter, but that it might be grounds for a person to withdraw their guilty plea.
But as far as section 7 is concerned, it was at issue in the Lyons case, as it is in the current legislation. What we have now is constitutional and it works. So then why start something which might provoke a debate which will go on for years before prosecutors can actually use it?