Technically, you didn’t trade Fluttershy herself, but rather her services as a pet trainer. And besides, Fluttershy willingly agreed to offer her services in exchange for the book. Nobody was forcing her to do it.

@Background Pony #7425  

Princesses are the master and your friends are your slaves

@Background Pony #0CE1  
Exactly. Mind, it wasn’t hers to trade away, so it’s… Well, I dunno really.  
It’d be either fraud or breach of contract (depending on RD’s knowledge and intent) if Fluttershy refused, but she didn’t.  
And it wasn’t like there was that much coercion.  
If we assume Fluttershy’s shy-ness isn’t considered strong enough to be relevant to the law (as in, if we treat her as entirely sane, rather than potentially suffering some anxiety disorder or such), I’m not sure there was anything illegal about it; Fluttershy went along with it with no threats or other coercion (RD didn’t even realize what she was doing, so of course she couldn’t pressure her)  
The trade or sale of services is entirely legal; It’s called doing a job. In this case, payment was to be given up front, but that’s fine as far as I know (just rarely done for jobs like these)
 
Of course, this is Equestria, whose history books go back to a time when the pony races were at war.  
If they ever had slavery, I would expect them to have it back during the times of the Windigos.  
In our world, meanwhile, we haven’t had slavery for ages (excepting America, but American slavery was somewhat different from pretty much everywhere else)  
Point being, Equestria might have far more detailed, and modern, laws regarding what is and isn’t a slave.  
The ‘they’re just hired workers’ excuse might have been a well-used loophole back in the day, before it was closed with stricter definitions of what is and is not a legal work-contract.  
So, while this’d not be slavery for us, it might be too close for comfort to a race who dropped slavery more recently (again, exempting America and other outliers)

@Background Pony #0CE1  
In dog training.

Technically, she just traded Fluttershy’s services. For possibly several years.

@Background Pony #5EBC  
Gilgamesh will have none of your shit

OH.  
SHIT.  
SHIT WHY DIDN’T I NOTICE THAT DURING THE EPISODE.  
FUCK. CAPS LOCK BECAUSE THIS IS IMPORTANT SOMEHOW.  
SHIT FUCK. SWEAR WORDS.

@G.S.  
She’s the ruler of a feudal society. She’s allowed to make rulings like this.
 
@cheezedoodle  
It’s indentured servitude if they volunteer. Which is still illegal now in most places, so depends on Equestria.

@G.S.
 
book or two *on

GTFO Twilight, you’re not qualified to be a judge. You need to be trained. Reading a book or two Equestrian law does not qualify you to practice it.

@Dawn Blast
 
The charges could be interpreted as trumped-up charges of slavery and trafficking.

How is this beign a Tyrant

Sorry, >>604797 gave me PTSD and drove me to drink. Now I live in a van down by the river.

I like “judgment mode” Twilight!  
( ͡° ͜ʖ ͡°)‎

@cheezedoodle  
It’s just a joke.

@cheezedoodle  
“I don’t like jokes”

At least it’s not :

 
It’s not slavery if you volunteer for it.

more Dashie getting arrested? i like it
 
you better surrender to your princess, Dashie >:)

@unknownguy777  
I think “[character]fag” might refer to an excessive/eccentric/overzealous fan. Not sure though.

@unknownguy777  
I see. I had a feeling, but I guess I ignored it. :T

@thps48  
“Flutterfag” is what Fluttershy fans/fanboys are called on /mlp/ so I don’t think he was meaning that.