The vigilance recommended in this quote is on the part of the people AGAINST ENCROACHING POWERS OF GOVERNMENT.
You are correct, but you might also consider that the Fourth Amendment protects us from UNREASONABLE search and siezure. It should also be noted that since the Prez is ordering these Outside-FISA intercepts, there is a record of them and others are privy to the info. Even without the at-the-moment court interaction, there is still a modicum of checks by virtue of the others knowing and a record of the orders. If the Prez did/does anything wrong or illegal, there will be a trail by which to hang him. Those doing the Chicken Little act are very aware of this and would be using more specific attacks if they thought they had any real ammo. There is still a dearth of information on citizens who have had their rights violated and we all know it would be headlined in the largest possible banners if there were any such folks.