Found:

Vacuous Movement Hypothesis

SYNTAX: the hypothesis that movement is blocked unless it affects the (linear) order of the string it applies to. EXAMPLE: this hypothesis entails that the wh-subject in who killed her? is not moved to the specifier position of the CP (as is the standard assumption for wh-questions), but remains in situ.

LIT.	Chomsky, N. (1986b) George, L. (1980)