In this experimental study, we focus on the following semantic universal: if a habitual clause reading, then generic pronominal subject; if an episodic clause reading, then specific pronominal subject. We argue that although this set of two conditionals is a universal property of all natural languages, English-speaking second-language (L2) learners of Spanish must access it through the mediation of aspectual morphology. Because habitual and episodic readings are encoded by different functional morphemes in English and Spanish, the L2 acquisition of this semantic universal necessitates a significant restructuring of the native form-to-meaning mappings. Even more problematic from a learnability point of view is the negative constraint on generic pronominal subjects in sentences with the Preterite. We compare the acquisition of the universal computational mechanism and the negative constraint with acquisition of the prototypical habitual and episodic meanings of the Spanish Imperfect and Preterite with dynamic predicates. Our findings indicate that advanced and even intermediate English-speaking learners of Spanish are significantly more accurate on the generic and specific subject interpretation purportedly regulated by a semantic universal and on the negative constraint requiring specialized syntactic computation than the prototypical habitual and episodic meanings usually taught in language classrooms. We argue that L2 learners have access to semantic universals and how these interact with movement at the syntax-semantics interface even before full acquisition of target form-to-meaning mappings. Our conclusion is that L2 acquisition of aspectual syntax and semantics is regulated by domain-specific constraints.