The expression 'with a vengeance' is used to emphasize the degree to which something occurs, or is true. He could have written, 'he will pursue relentlessly' - he will pursue, track down these criminals using utmost effort.
The expression 'to the hilt' means 'completely, totally,fully' - they will be charged with every law they have broken, and they will ask the judge for the maximum punishment for these crimes that the court is able to hand out.
'elements', referring to people, refers to a group of people of some particular kind within the general population.
So- 'criminal elements' means the group of criminals that we have within the general population of law-abiding citizens.
'trafficking' is dealing or trading in something illegal; and instead of, say, drugs, these criminals distribute and sell obscene pictures, magazines, books -that is pornography. (Or perhaps, they operate pornographic websites on the Internet)'
Yes - certain kinds of 'explicit adult material' (pornography) is quite legal to sell to adults. However, brutal, sadistic material; material relating to animals; and child pornography etc...No.