Even a "priest" or "nun" would be okay on the law-keeping side, in the sense that they are supposed to be defending the peace in another way, through morals etc, and should actually be trying to stop crimes/immorality, but instead they fall for someone immoral who is on the wrong side of the law.
Oh and I'm not just looking for a one-time criminal or something... Like, a kid that gets caught shop-lifting just once and falls for the lovely cop that catches him and reforms himself. Nope! I'm looking for a career criminal, someone that regularly commits crimes and isn't easily reformed (if at all).
Similarly I'm looking for a law-keeper/protector who does this specifically for a living, like it's their job and their responsibility, their way of life. That's why it's so shocking/interesting when they get into a relationship with someone breaking the very laws that they are bound to protect.
Any genre is okay, but I honestly favor shoujo/josei or BL.
Examples...
MW - priest/serial killer.
Honto Yajuu - yakuza/cop.
Thief and Detective - what it says.
If it's for you, no matter how far... - also thief/detective.
Madness - yet another priest/mass murderer romance.
Missing Code - art thief/(spoiler).
From Eroica With Love - art thief/NATO agent. One-sided, but still...
God of Dogs - a bit unclear, but at least one of the cops is involved with a juvenile delinquent who is now doing jail time.
Thanks to anyone that helps.
) 
, and I still can't get enough of it. 
