。
Those who break the law will be punished.
Literal
Law [object-を] violate one-[者] [topic-は] punish-[passive-される]
The formal/literary noun 者 (もの) means 'person, one' — more abstract and official than 人, typical in legal, institutional, and written contexts. 法律を犯す者 = 'the one who breaks the law' (a generic relative clause). 罰せられる is the passive of 罰する.