Previous work has demonstrated the possibility of stabilizing plane wave so
lutions of one-dimensional systems using a spatially local form of time-del
ayed feedback. We show that the natural extension of this method to two-dim
ensional systems fails due to the presence of torsion-free unstable perturb
ations. Linear stability analysis of the complex Ginzburg-Landau equation r
eveals that long wavelength, transverse wave instabilities cannot be suppre
ssed by the method of extended time-delay autosynchronization. The conclusi
on follows from symmetry considerations and therefore applies to a wide cla
ss of models with simple plane wave solutions.