I just posted this on another forum where a similar discussion is happening and thought it would be relevant here:
A young green dragon has been getting his sycophantic kobold followers, enslaved lizardfolk and ogre minions, and a mysterious nothic ally to raid settlements and caravans for treasure and people to eat. The party was tasked to take care of the threat by the nearby city, assuming that this band of vigilantes would slay all these monsters.
Weeks later, the Lawful Good party returns to the city with a caravan of arrested monsters suspects who had attacked them on sight, despite the party requesting that the suspects peacefully turn themselves in for questioning. Now the city has to figure out how to securely detain and feed a large, poison breathing dragon, two ogres, a nothic with dangerous gaze abilities, and dozens of other suspects. Evidence has to be collected, witnesses found, defense attorneys have to be assigned to the dragon and other creatures, trials have to be held, you've gotta figure out if it's even the right young green dragon or if some of the arrested kobolds stayed home while others went on the raids, etc.
Going by the laws of the Clovis Concord detailed in Explorer's Guide to Wildemount (laws which do not include capital punishment even for murder), let's say the young green dragon stands accused of:
- theft in the amount of 85,000 gp
- 15 counts of slave ownership
- failure to pay taxes
- 10 counts of damage to private property
- 5 counts of assault with intent to kill
- 22 counts of murder
If judged guilty on all counts, the young green dragon faces:
- 200,170 gp in fines
- repossession of wealth equal to unpaid taxes to the Clovis Concord
- 222 years, 195 days imprisonment
Even assuming that this young green dragon is six years old, the beginning point of its age category, by the time its sentence is over it will be 228 years old and in the adult category. At this point the now adult green dragon will possess lair actions while in his prison lair (summoning grasping roots, thorny bushes, fog that inflicts a short term charm affect). In addition, the region within a mile around the prison lair will spawn thicket mazes, and the adult green dragon will be able to see and hear through the eyes and ears of rodents and birds.
So if the Clovis Concord is really serious about applying the law equally to a captured dragon, they'll need to construct a special prison in anticipation of the abilities their prisoner will eventually develop. Then they'll need to pay to keep the dragon fed for over two centuries. Even if the dragon doesn't escape on its own and isn't broken out by dragon-worshiping cultists or whatever during that entire time, what happens when the now adult green dragon's sentence is up and by law is free to go? Is it going to be a reformed Lawful Good adult green dragon, is it going to relish the newfound freedom to exercise the power it has gained as its grown to immediately go on a rampage, is it going to go off somewhere and amass an army to raze the countryside while it searches for its captors' descendants to systematically slaughter them?
Realistically, I imagine that dragon is going to be mysteriously assassinated in its prison before it reaches the adult age category.
Thinking more about it, considering that metallic and chromatic dragons both are very proud creatures that covet treasure, being imprisoned by "lesser beings" and denied the ability to amass treasure would be an overwhelming source of shame that could drive a dragon mad.
Frankly, considering how much money and space keeping a single dragon imprisoned and fed would require (not to mention the martial and magical power needed to stop an escape attempt), I can't imagine it happens often at all, even in a place like the Clovis Concord where there is no such thing as capital punishment.
Maybe metallic dragons take this responsibility? Maybe they are apprehending and maintaining prisons for evil dragons somewhere?