The present study examines the claim that definite relative clauses in Modern Standard Arabic exhibit free variation between resumptive pronouns and gaps. The implication of such a claim presents a problem for minimalist syntax that does not tolerate true optionality. To solve this problem, the study argues that the original claim is incorrect and that despite similarities in the PF outputs, resumptive relatives are syntactically different from gapped relatives. While the latter is derived from a standard VSO structure, I propose, the former is derived from a topic-comment structure that already contains an RP. Thus, the fact that resumptive relatives contain resumptive pronouns has nothing to do with relativization, as is generally assumed. The study demonstrates that both resumptive relatives and gapped relatives are derived by movement in contexts that do not involve islands. As it turns out, resumption in relatives is used only as a last resort strategy to save structures in which movement is genuinely blocked, such as islands, from crash. Altogether the study concludes that the variation observed does not reflect true optionality, a finding that supports robust economy principles of minimalist syntax.