Samoan (Polynesian, Oceanic, Austronesian) nominalizations exhibit an exceptional tri-partite/inactive case alignment which distinctly marks unaccusative, unergative, and transitive subjects: while unaccusative subjects are marked by inalienable possessive case, unergative subjects are marked by alienable possessive case. Transitive subjects instead maintain their ergative case marking. Recently, Hopperdietzel & Alexiadou (forthcoming) argue that the observed tripartite/inactive case alignment follows from the prepositional nature of transitive subjects in Samoan (cf. Polinsky 2016). Transitive PP-subjects therefore obey the unaccusativity requirement on nominalizations (Alexiadou 2001), contrasting with unergative DP-subjects that must be base-generated in the nominal domain. In this talk, we provide additional evidence for this account from Samoan subject clitics which, in nominalizations, exhibit a marked unergative alignment: while unaccusative and transitive subject clitics are marked by inalienable possessive case, unergative subject clitics are marked by alienable possessive case. Developing a non-uniform analysis of clitic pronouns (cf. Bleam 2002), we demonstrate that only unergative subject clitics must be both thematically licensed and case-licensed in the nominal domain, which highlights their special status in nominalizations. Consequently, the marked unergative alignment of Samoan subject clitics further supports a prepositional account of syntactic ergativity and the unaccusativity restriction on nominalizations.