... But still the fact that there's no way to game the system just feels off
There ARE ways to "game the system," such as Warden Swords (which you noted yourself). The Blackstaff is another.
Offhand, it strikes me that making a deal with some magical being (who isn't subject to the Laws) is another. From a legalistic standpoint, the Wardens may come to snickersnack you anyhow, if you're hiring murder from the fae (or whoever... or
whatever!) but I don't think it's the same sort of soul-staining "black magic."
... You can't use enchantment or any sort of lethal force or even Transformations even if they would be beneficial or at least considerably less lethal ...
Actually, I suspect this of being an "unintended consequence." Jim figured out the principals of Dresdenverse magic, then realized that the violation-of-Self that is a forced-transform would be a violation of the Laws. He still got Lea to do it in the Yucatan, of course... But as noted, she's one of those "not subject to the Laws" beings.
Or maybe I'm mistaken, and Jim wanted this to be specifically illegal. IIRC, Jim has stated that he's going to have Harry break
every single law before the books are done. I'd
love to read the scene where Harry transforms the entire White Council into a flock of fluffy white sheep...
... As an example you're not supposed to invade the mind of the other but the Merlin was able to do that whole communication spell when Peabody attacked ...
I suspect there's some sort of loophole for a 1-way projection which the recipient perceives as a normal sensation, i.e. audio. The wizard isn't doing any mind-reading, which is explicitly verboten, and isn't imposing his will on the victim, which is also verboten (not imposing his will any more than he would if he were speaking verbally). It was a virtuoso performance by the Merlin, a sort of "trick shot" that few-to-no other wizards could have duplicated (maybe (
eventually) Molly?).
... In addition to the spell that Elaine and CarrieHarry have used since their youth.
...
For instance if someone said I want to quit smoking they will probably allow you to walk into their mind figure out anything you could in order to make them stop smoking ...
Elaine & Harry used it willingly and mutually: both were aware, neither was a "victim." There was no "invasion" or subversion of the will -- those are the critical components that make black magic so bad.
I expect smoking-cessation to be right on the fringes, and easily stray over the line. Remember that what Molly did was try to cure drug addiction! So if you go spelunking around in someone's mind to "figure out anything," that may be a problem; free will is a critical element in the Dresdenverse. If the addict later
wants a cigarette (or vape, or whatever) and your spell keeps them from doing it... you have impeded their free will. It's not just a matter of the wizard getting some "open sesame" magic words to agree to this; that's more a faerie condition. Humans
get to change their minds, and your spell prevented that; the effects are liable to be just as bad as they were for Rosie and for Nelson.
... just saying please go away I don't want to deal with this s*** ...
Yeah, this is 100% black magic, right there. It's imposing your own will directly on another mind, taking away their own free will. And for what? Some petty annoyance...
The Wardens will be with you shortly.
... he use body magic in order to make him move really fast but killed with an ordinary knife ...
I think you're correct in this; it's black magic (or at least black-ish, very-very-dark-grey).
... Seems like just as much of a hotfix as the warden's swords that dispel magic but it's the edge that kills you.
That's very different. The sword, when it kills you, kills you identically to any sword: completely non-magically. The dispel-magic effect just strips away your magical (non-natural) advantage.
The guy who used magical speed was getting a non-natural advantage in doing murder. It may not have been magic that proximately killed, but the kill was aided and enhanced by magic, in a way that could not be naturally achieved.
... My personal consideration is shape-shifting. I shape-shift myself into a hippo and then I murder almost everybody I can with this top-tier murder Beast that was considered more mythical and dangerous than some dragons
I have directly use magic in order to kill someone that is to say the entire alternate form so am I tainted or not? ...
Again, I think you've captured it well. And yes, this is black magic.
Will & the Alphas aren't black-magic-tainted because when they go for a kill they are fighting non-humans (well, OK -- they do
threaten some human wizards; but never IIRC kill any). In Fool Moon, the other werewolves are actually killing people, and (if a Warden came visiting) would thus get snickersnack'ed.
Considering the danger of using direct for spells surely there's got to be a class of medication that at the very least makes it so that you can fight mortal opponents and don't end up running the risk of going cray cray.
If you could get a medically & scientifically trained wizard, that seems like something that could
MAYBE be done... if you could find a medicine that effect the soul... OTOH, I'm not sure the White Council would be at ease with the idea of taking a pill to be able to break the Laws. The potential for abuse looks WAY worse than the upsides.
... that rope trick that set up a sex scene as the basis for Ward's or evocation fighting style for when he's outside his office but doesn't know if he's up against acceptable targets
Agreed: immobilizations look like a great option that Harry under-uses (but as to the specifics of those ropes, they were specially prepared and IIRC only usable within the confines of Harry's own home -- he stated that he'd need more experience before he could craft something usable anywhere).
But we saw in Small Favor (in the scene fighting Tessa) that Harry now has at least some ability to manipulate chains & such; so presumably he could, with practice, do something that would more fully entangle a foe.
I think ordinary ropes look like an "iffy" proposition, though: looping around someone in a way to genuinely immobilize them is kinda tricky, then tying a knot remotely is another level of fine control. These aren't Harry's strong suits! And while he's focused on tying up the mortal, anyone else is free to blindside him.
Some sort of pre-enchanted rope might work; or rather a set of them: carry a few lengths of rope all "tangled" together, throw them at the target and they automagically untangle, into half a dozen or so lengths that swiftly tie the target at ankles, knees, wrists, and elbows (with no attention needed after the initial throw). Although Harry seems to have less talent for working subtle & sophisticated magics on the fly, his enchanted items are really above-par, including subtle & sophisticated magic!