。
I'd like to exercise my right to remain silent.
Literal
Right-of-silence [object-を] exercise [quotative-と] think.
黙秘権 ('right of silence') is a Sino-Japanese legal compound — 黙 (silence) + 秘 (secret, conceal) + 権 (right). 行使する is the formal/legal verb for 'to exercise (a right or authority),' more elevated than 使う. The frame ~たいと思います is a softened, polite way of expressing a wish — 'I think I would like to X' — very common in formal or careful speech.