I'm thinking about going through all the ZM maps at some point and compiling a big fucking list of this-should-be-illegal cade spots, but until then (or until the illegal cades forum is more populated) it really comes down to admin opinion, and if they don't like it, well, Your Mileage May Vary..

Typically when I find people cading "illegal" spots (which are often very clever!) I just get right up next to them (freeze if necessary), talk them through how its illegal, and suggest to not do it again next round or face mostly mild consequences. Moving people to spec (Kenny: ma_spec [Nickname]) is usually good enough.