。
I would never break the law.
Literal
I [topic-は] never law [object-を] break [nominalizer-こと] [topic-は] not-do.
決して~ない ('never, by no means') is a strong negation adverb that requires a negative predicate. ~ことはしない ('would not do [such a thing as]') is an emphatic way to deny an action — nominalizing the verb with こと and negating する. Double emphasis on the refusal.