Clarify effect of link stealing within a single connection

Question about link stealing from Lorenz Quack:

"The spec says that a link can only be active at one connection at a time and thus goes on to introduce link stealing (2.6.1). However it does not specify (at least I did not find it) what the behaviour should be when a session on the same connection tries to attach an already attached link. Should it steal it? should it be a LinkError?"