All very good questions.
Certainly, lots of the standard crimes are illegal--murder, theft, etc. The police gather evidence and arrest these criminals, they go to trial, the judge decides their guilt, they go to prison or the chopper's block. This is relatively straightforward.
Then there are the hard-to-prosecute crimes like bribery. Bribing the police is illegal, but is probably quite rampant. Bribing a judge is also illegal, but a judge decides if you are innocent or guilty.
Enslavement of citizens is also against the law, whether through magical or mundane means. Although there are not specific drug laws, there are laws against contributing to the general lawlessness, prevention of gainful production, and other such charges which can be trumped-up charges as much as not.
A famous catch-all trumped-up charge, although archaic in this enlightened age, is witchcraft.
Punishments run the gamut from imprisonment, death, the stocks, the lash, fines, fees, and the like. If you're important enough that they can't afford to kill you, but also you do something bad enough to be worth the expense, magical geasa and curses may be used--but they are rare and rather scary to the public at large. Exile is not typically used.
Torture? Torture is a bad and evil thing, and something no respectful member of Paridon's fine constabulary would ever commit. In fact, suggesting that they would is an act of sedition and illegal. Such terrible people who would dare sully the good name of the constabulary are removed for the good of society.
The judge decides on the sentence for the guilty, but will definitely take the police's views on sentencing into consideration. All in all, the police and judiciary have broad powers to prosecute at will. However, Paridon is a city of free thinkers, where the enlightened have freedom in sophisticated ways that the countryside would not understand.
* * *
The big thing to keep in mind is that evil can be found everywhere, within the constabulary included. There are plenty of laws on the books to cover all sorts of situations. You can charge Alek with anything you like--the trick is to make the charges, and him, stick. Of course, you should also let your moral compass be your guide. You could, for example, arrest, say, Marionette as the clocktower murderer, creator of the artificial vampire, general lawlessness, witchcraft, etc., and you might be able to convince a judge to go along with it, convict her, and sentence her to Darian's custody. But that would be wrong.
The police power you wield is very real, and very strong. But with great power comes great responsibility.
Or does it?
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