User blog comment:Alchimous/Teleportation Matrices/@comment-4536066-20121004185732/@comment-4536066-20121004190135

Another question, though:

If someone attempts to teleport into a blocked area, where do they end up? The worst case scenario, I think, would be that someone casts the spell, gets into the abyss, and then can't proceed from there and is stuck in the abyss. ... Which is not good, if little farmgirl Janey didn't bring a second teletab to teleport her somewhere else. #abyssaldemons

Best case scenario, I suppose, would be that the law magic opens both portals before sending you through either one and if they don't both open, the spell just fails and you're short one teletab.