The Outer Gates are what keeps the world safe from such things, what locks them away and keeps them outside—and thus, such things are called Outsiders. They are so alien, so not of this world, that few methods of assault stand a chance of giving them more than a moment's pause. And the intentions the Outside has for us are so dark, so dire, that the Seventh Law is the only one on the books that isn't conditioned upon casting a spell. Even doing research on the Outside is verboten, setting aside actually pulling power from there.

The Gates are never fully closed. It's through the tiniest of cracks that the darkest of things come into our world (like He Who Walks Behind). And when someone does pull power from there, forging a bond with a malevolent Outsider force, one of those cracks widens, just a touch. The human race is lucky that few have ever managed such an effort for long, thanks to the efforts of the White Council a particularly zealous enforcement of the Seventh Law.

The Gatekeeper's Job Description

As much as the Gatekeeper watches over the flow of time and those who would meddle with it, such actions are really a side-project, related but separate from his main duties (as you might guess from his title). The Gatekeeper is our first line of defense against the Outsiders, performing perhaps the most important job in all of Creation. At the least, he maintains the alarm spells that shriek when the Gates budge, spends the lion's share of his time walking the Nevernever looking for signs and portents, and may even act as an "off the books" emissary for the White Council with the major realms of the Nevernever. The Merlin may lead the White Council, but to many supernatural creatures, it's the Gatekeeper who truly speaks on its behalf and commands the greatest respect.

If anyone knows how the Outer Gates came to be in the first place, they're not talking.

In your game

Actually drawing down power from beyond the Outer Gates, in full intention and knowledge about what that means, is a pretty villainous thing to do. Even if you aren't fully apprised of what you're doing, this is the kind of ink-black magic that will stain your soul right quick.

This doesn't mean that the Seventh Law can't be relevant for players. The biggest villains of the Dresden Files may well be tapped into some kind of Outsider mojo, so there is, at least, that; and while the Gatekeeper is our cosmic First Responder for matters involving the Outside, he has been known to tap others from inside and outside of the Council when things are particularly bad.

But players can also stumble across the Seventh Law, thanks to the particulars of its wording—namely, the prohibition against even researching the Outside. A GM looking to put a particularly nasty choice in front of her players could easily "hide" a piece of knowledge within a forbidden tome of Outsider lore. And if a life is on the line, isn't it worth the risk? (The Outsiders certainly hope so.)

Does Demon Summoning Break the Seventh Law?

The answer is: usually not. Compared to the Outsiders, most demons a wizard might summon are comparative "locals", though they might have plenty of notions about how it would be a grand thing to hoof it on over to the Outer Gates and kick them open with a big welcoming party.

It's still risky. Many times, Outsiders have masqueraded as standard spirits and demons, so the White Council tends to frown on summoning them unless they are quite confident in your competence and judgment (and how often does that happen, really?). As a rule of thumb, the Council sees it as a privilege allowed its own members, but off-limits for the rest of the supernatural practitioners out there. So even though it isn't directly in violation of the Seventh Law (or any other), the Wardens get real antsy about amateurs messing around with summoning. Even non-Outsider demons are dangerous in their own right.

Think of this as licensing on explosive compounds. If you know what you're doing, have a legitimate reason for their use (construction, demolition, mining, etc)—and you know how to be cautious, you can get them, even if you aren't someone military, and you'll have official (if occasionally supervised) approval to use them. If, on the other hand, you're just some guy who likes storing a few kilos of plastique in his garage, the authorities are not at all amused to find out about you.

The Blackstaff

The Blackstaff is both the name of an artifact of great power and the nigh-secret office filled by an experienced member of the White Council (sometimes, but not always, a member of the Senior Council him or herself). Alone out of all others, the Blackstaff is given leave to break any and all Laws of Magic in order to take down the Council's most dangerous enemies. No higher position of trust is accorded anyone in the White Council, though the Gatekeeper may be considered a peer in that capacity. Unknown to many, the current Blackstaff is not uncoincidentally Harry Dresden's mentor and surrogate father-figure, Ebenezar McCoy.

But what does the actual Blackstaff—that dark length of gnarled, spellcrafted wood—do? Theories abound. Perhaps it acts as a "filter", somehow preventing the violation of the Laws from having the usual darkening effect upon the spellcaster. Or maybe the spellcaster faces those as anyone would—but the Blackstaff prevents his transgressions from affecting the natural order at large. More exotic theories can be proposed—anything from the Blackstaff being a semi-sentient familiar to a bound up Outsider itself—but in the end, its very existence is a guarded secret, and for anyone other than the Blackstaff, looking into its origins might be taken as a violation of the Seventh Law by itself...