It's the government's responsibility to crack down on violence.
Literal
Violence [object-を] crack-down-on [nominalizer-の] [topic-は], government [of-の] responsibility is.
取り締まる ('to crack down on, to regulate, to control') is a compound verb: 取る + 締める ('to take + to tighten'). Used for policing, regulating, enforcement. である is the formal copula. A statement of civic principle.