It is well-known that certain syntactic properties constrain ellipsis (e.g., voice marking, argument structure) while others do not (e.g., movement out of islands). Based on a cross-linguistic survey of sluicing constructions (featuring data from Aklanon, Chamorro, Kaqchikel, Malagasy, Nukuoro, and Nupe), I observe that argument extraction restrictions, like islands, fall in the latter category: there is no known restriction on argument A'-extraction that persists under sluicing, which I term the sluicing-extraction generalization (SEG). I argue that the SEG is not appropriately captured by recent weakened syntactic identity analyses (e.g., Ranero 2021), which fail to account for the breadth of the generalization. Rather, I show that semantic accounts like LF-copying (Chung, Ladusaw & McCloskey 1995) do well in capturing the complete lack of movement restrictions under sluicing. Additionally, I argue that this account can also capture the voice mismatch data, which has previously been used as evidence for strict syntactic identity.