Sluicing, as described by Ross (1969), Chung, Ladusaw, and McCloskey (1995), and Merchant (2001), ameliorates island violations. In this paper, I identify constructions in which sluicing does not ameliorate island violations. I conclude that islands inside of left branches will not be ameliorated by sluicing. I then use this generalization to develop a diagnostic for left branch positioning and apply this diagnostic to various controversial structures.