I'm going to provide a dissenting opinion here. There are two main reasons the laws of magic *shouldn't* be applied to the character you've described.
The first reason is in character: The way mortal practitioners work, they have to absolutely believe in what they're doing. That's where the lawbreaker powers come from - if you kill with magic, that requires a self-image as someone who kills with magic.
Sponsored magic doesn't work that way: it's more like someone gave you a gun - killing with it is bad, sure, but it's not Bad to the level of applying lawbreaker stunts. (Note: There is a great deal of debate on this point, and it's overall probably pretty iffy. See, for example, the discussion here:
http://www.jimbutcheronline.com/bb/index.php/topic,18574.0.html where there's a fair amount of discussion, some good ideas, and absolutely no definitive answer.)
Think of, for comparison, these examples:
A faerie knight uses summer magic to kill someone at the order of his queen. Does the knight need to worry about the laws of magic? I would say no; he's not using mortal magic.
A shaman has cut a deal with a fire spirit, channeling (fire) to represent this. She asks the fire spirit to burn a couple of thugs that are attacking her, and the flames kill them. Does the shaman have to worry about the laws of magic? I would say partially - it's not her power, so no lawbreaker stunt, but the wardens are probably going to be interested...
The second reason is out of character - essentially, you're telling your player "Here, you can buy this four point sponsored magic. But if you ever do anything with it, you're going to have to buy lawbreaker stunts, and if you use it three or more times you're going to have to start changing aspects." Remember, necromancy itself is against the laws of magic; if this character has to work within the laws, they're paying an awful lot of refresh for something they can't effectively use.
As an alternative, consider just giving the character, say, a trouble aspect of "Walking Necromantic Battery" - they can invoke it to generate minor necromantic effects, but mostly it's going to get compelled to, say, wilt plants nearby, or have necromancers come try to use the character in some ritual, or have wardens show up to try and destroy the character so that they can't be used in anybody's ritual, or... etc.