Why not go to the source and ask your question? Stop by an inspection facility, or your State Highway Patrol, and ask what is intended by the law regarding "lowering" a vehicle. What do they mean by "lowering"? Is there a tolerance, of say 90% of factory specified height? Do they have an official list of "factory height" (usually it is "bumper heght")?
The State must have some standard to go by, or else how would they know whether or not you are in violation of the statute prohibiting "lowering" the vehicle?
The above post is correct about all States being a little different in their Motor Vehicle Codes (laws). The few States that I am familiar with prohibit lowering the vehicle to the degree that it affects handling and other safety factors. If you install struts and springs that are intended to replace "factory" parts, and not specifically intended to "lower" the vehicle you should be OK.
That having been said, you still should ask an "official" what is the standard used in appling the law. An inspection station should have a list of those standards for every car subject to inspection, otherwise how do they determine if you lowered the vehicle? Do they just guess, or does the inspector use his/her own judgement?
You need more information. The State should have its laws posted "on-line". Go to the State web cite and look for your State's Motor Vehicle Code, and look for the laws regarding "modifying" a motor vehicle, or "prohibited vehicle modifications", or something along those lines. Once you know what the law is, then you can determine if your planned modification would be in violation of those laws. rangerj