The two opaque domains are: (1) the subject of a tensed sentence (the Nominative Island Condition: NIC); (2) the c-command domain of the subject of an NP or S (the (Specified) Subject Condition: SSC). These two binding principles have a wide range of application, and relate in an interesting way to the theory of movement in that the transparent (non-opaque) positions within clauses are those from which movement is free out of the clause (namely, COMP and subject of infinitive).
- Chomsky (1993), a pag.153