Thanks for asking.  It depends.

If you leave the country to aid and abet the enemy in killing our troops and those of our allies, you should forfeit your claim to citizenship.  If the law needs to be changed to enable it, then let's change the law.  But after reading the article, perhaps the existing law already enables it--as long a there is a hearing wherein the individuals have the opportunity to defend themselves.  

Our laws do not provide a hierarchy of citizenship rights....Canadian-born citizens have the same rights as those who were sworn in.  So if the latter can have their citizenship revoked, why not the former too?

If you stay within the country to aid and abet the enemy, that's treason too, but at least we can imprison you and hold you to account.

But once you leave the country to fight against our country, it is ludicrous to subsequently hide behind the protections of our flag and citizenship once caught by the Americans.  You made your bed, now lie in it.