This paper is primarily concerned with the syntactic and semantic properties of two focus particles in Japanese, koso and sae . Occurrence of these particles is shown to be licensed by the head of a clausal category they take scope over. The licensing relation in both cases is subject to island constraints on movement including the Complex NP Constraint (CNPC), suggesting that it is an instance of the movement operation constrained by UG. Both particles can, however, escape from the effect of CNPC with essentially the same mechanism, under the same principles of UG. The mechanism appears not specific to constructions with these particles but more general, applying to apparently different constructions involving wh .