The switch has to be on a wall, but there is no rule about which wall. Specifically, the rule does not require that the wall switch be in the same room as the wall-switched lighting outlet.It means a switch on the wall for lighting purposes.
From a language perspective, the phrase "wall switched-controlled" functions as an adjective that modifies the noun, "outlet." It tells us something about the outlet. But the essential sequence of words is, ". . . outlet . . . in . . . room." The meaning of the sentence does not come from the sequence, ". . . switch . . . in . . . room . . . "