China doesn't need to keep them locked up. China has the largest rate of organ transplants in the world, the highest rates of executions (actual number a state secret) yet has low rates of organ donors with trial registration schemes only starting within the last decade. Guess where they get the organs from.

Journalists investigating the suppression of Falun Gong estimated that approximately 60,000 convicted members were executed and their organs harvested. People are routinely arrested and never heard from again. In some cases families have been told a relative was executed years previously, but often they hear nothing at all.

In 2008 China's own deputy health minister estimated over 60% of transplant organs were sourced from prisoners, but Chinese officials have clamped up about this in recent years. They have occasionally said that this source of organs has been excluded, but there's no way to verify this as rates of donor registration aren't known, rates of executions are a state secret and none of the people or facilities involved are known or open to investigations.

So yes, sure, just like the USA.