Yes, a ward would break a Law. Don't read this if you haven't read Changes yet, but Harry had to disable his wards for when the FBI broke in, otherwise it might've killed them. Which is bad.
You can tie a Ward to prevent certain things, if you have something of that kind of thing. Get some Red Court ichor (not sure if it is actually blood) and you could make a ward that stops them alone. I suggest going on a monster killing spree, gathering samples for your wards. Get some ghoul blood, Red ichor, etc. Tie them all to your ward, so that you don't have to worry about killing someone. Add a nerfed ward as well, that works on humans and whatever you missed in your uber-ward (immobilization could be good).
Something just occurred to me. If you think about the laws as less laws of the physical universe and more laws of human behavior this makes a lot more sense. Think about it this way.
Your wizard's wards accidently fry some insurance salesman. Now you're upset and you try to rationalize it so that you don't have to deal with the harsh reality that you just took a valuable human life. So you think "It was the wards that did it. If he hadn't knocked extra hard on the door he would have been fine." So the next time you are in a fight you think "Well, maybe I can create an offensive shield. I'm still defending myself and they only die if they attack me." Now you're killing attackers on a regular basis and you still have to rationalize it, to make it ok. After a while of that maybe you start killing people before they attack you, when they start menacing you or pulling weapons, you're still defending yourself, so (in your mind) it's ok. More time passes and you see a lot of people die and maybe you start thinking "Well, clearly these mortals die so easily they can't be worth much, if one dies and it improves my life what's the big deal?" And then you're laughing maniacally while hundreds die before you.
This is the stuff Dresden stays up at night worrying about as he is a lawbreaker. He wonders if he even inadvertently killed people at the party in grave peril. Or if killing any FBI guys would further twist him.
I mean, one somewhat related example I noticed while rereading Changes today:
When Harry/Susan/Martin are raiding that compound in Nevada, at one point the mercenaries tries to shoot Harry, but his shield ends up bouncing the bullets back and hitting one of them in the gut. Harry doesn't even give him a second thought, even though that probably killed him.
So basically, I would only count defensive magic as breaking the first law if it's being employed with full intention of lethal consequences.
Something else to consider. Wards in and of themselves just reflect the amount of force projected against them, back at whoever/whatever was exerting it. Unless of course there are more shifts of force than shifts of Ward. Now 'landminds' can also be built into Wards, with Harry having done so some time prior to Dead Beat.
My theory on Changes:
Harry seemed to have the normal Ward, plus 'landmines' built in. Harry also seemed to have an additional 'layer' which could be activated, which could create an essentially inpenetrable barrier into or out of the Ward, until the next sunrise. The downside as mentioned in Dead Beat and Turn Coat is that while nothing could get into or out of the rooming house Harry lived in, the building itself could still be set on fire, which would be a problem if people were trapped in the building by the Ward. In Changes, Harry had Bob completely drop the Ward because the 'normal' way law enforcement conduct a raid (with a battering ram) would likely have triggered several effects from the Ward, amongst them having it automatically go 'up' denying entry or exit for a day.
The way I look at this is that it IS complicated and full of gray areas. Not just in terms of rules mechanics but also for the in-universe characters themselves. This is probably one of those topics that you could hear a room full of Wardens in Edinburgh discussing/arguing over late at night over drinks. I suspect this is also why you do not see very many wizards living in close proximity with mortals. Especially the more powerful ones.
From the novels, we don't know a whole lot about where other wizards actually live. We know McCoy lives on a farm in a very rural area. Simon Pietrovich, the former, assumed dead, member of the Great Council lived in a tower/compound in Archangel. I'm assuming this tower was not in the city square or anything.
Again, look at the novels. As Harry grew as a wizard and got more and more involved in the bigger league stuff; his apartment and the civilians/mortals around him became more and more of a liability to him. I have always seen this as a major theme of the novels and I see that as well in the RPG.
The common myth and legends of wizards have them living as mysterious hermits in far removed places surrounded by folk stories of bad things happening to those that wander to close. Perhaps for a good reason.
Council is a bit overly jumpy, they might decide you are a law breaker (though a soulgaze could change their mind, I think). In game terms, you don't get lawbreaker though, and that's far more important than such petty issues such as whether you get killed over a misunderstanding or not.
Dresden's insistence on bringing down his Wards in advance of a police raid
Though someone could still explain that the guilt of causing such deaths would be sufficient motivation to give ranks of Lawbreaker.
Zombies in the books don't seem to be bringing someone back to life. Overall they don't seem to have much intelligence (and remember constructs have intelligence). I think we can come up with a lot of ways a zombie MIGHT be breaking the 5th law, but my point was that the books (novels or RPG) don't really clarify how they do this.
They do state in the books why zombies are against the fifth law. Because you are actually bringing someone back to life. That's why they need a heart beat.
Now, the thing is, is whenever I first read the thread, I immediately began thinking on the Archangel fortress, before its fall. ((btw, i haven't read past Small Favor yet, just to let you know)) It was stated that it was one of the greatest fortresses of mortal making every designed. And I'm not going to get into how its magical defenses where layered, prepared or anything like that. I'm just imagining to myself, a certain set of events. One doesn't really make a fortress to sit and look pretty in. They make it to protect themselves and their interests. Now the thing is, is they also don't make it, if they have no enemies. So, I would assume the Archangel would have come under assault under many occasions, from many different enemies. And, I would assume that the basic wards where among the most powerful ever crafted. Therefore, I would guess, that a decent number of would-be besiegers, many of which were probably fellow wizards, warlocks and or sorcerers, would have quite easily died at the hands of their own failed attempts to breach said wards. I mean, regardless of all the supernatural enemies out in the dresdenverse, or in any other supernatural setting, humanities own greatest enemy, will be others of it's own race. Simple as that.. So.. One would assume that the leader of the Archangel (whose name escapes me at the moment) would have technically fell very easily into lawbreaker status at one point, or another, in time...
As for Archangel I can think of one possibility but it involves post Death Masks spoilers. Perhaps the blackstaff is responsible for any deadly wards on any white council stronghold.