Using House Alarm Signs?

I just bought (on Ebay) some ADT House alarm signs (1 lawn sign and 2 window signs) but I dont have an actual ADT House alarm. I had read somewhere that just posting these signs in a good deterrant to burglars. After purchasing them, I realized that maybe posting them is illegal? But I cant find anything online about it. Can anyone tell me if it is, and if so, what would happen if I did display them around my house?