That's like saying locking people in camps is legal in the US. Technical not a lie, but a bit misleading.
Forced labor as a proportionate punishment for a crime you were found guilty of by a fair trial is not a problem in my book. We can talk about safety conditions, perverse incentives, whether the trials were fair or the punishments were just, etc. But the fact that we make a murder work 8 hours a day isn't per se some human rights abuse, in my opinion.