Extra Magical Cancellation
So magic is physics--it flows through everything binding it together, like a force...ok, wrong universe, THAT's a galaxy far, far way.
Point is, at all times, there's a BASELINE magical energy which is always present.
Extra Magical Cancellation targets anything off of the baseline. And it's dangerous, because if it's still being used when there isn't "extra magic" it starts siphoning off the magic of reality. It will start with life so a place where it's been used might look like a blighted plain, but will eventually will move on to the more fundamental aspects, like physics.
In places where there's been anti-magic vs. magic, you might end up with something like this:
A Stiffening of the Weave OR Pattern LOCK
In this version of things, magic is still present, but it's been frozen so that it cannot be manipulated, and thus, magic cannot be performed. Residual effects could mean that nothing can grow--or that anyone in this type of field actually never grows old--they can't die because the pattern is locked.
Cut off the spell
This method will likely rely on a sentient mind which can see magic--cutting out bits of the specific spell so that the circuit never completes. Or, alternatively, an anti-magic zone which is continually cutting little tiny holes in reality. If the pattern has been present for a while, it "heals" in a fraction of a second and bounces back, but if it is used and magic channeled through, there's a chance of it breaking forever. This is not a place you want to have a child--this method of zone, you'd want fully formed adults. Likely a place which messes with your mind. Active channeling is a bad bad idea in a place like this.
Ye Olde Classic Black Hole
Congrats. You have a black hole. Magic doesn't work, and neither does reality!!
Remember this is MAGIC. It's made of handwavium. As long as your system is internally consistent, and makes some kind of sense, you can do whatever you need to do.