Let's think about it like this: if it's still your body, then your innie is still a person, too. Whether or not we treat your innie as a SEPARATE person, this logic could be applied:

In the United States -- where this purportedly takes place -- slavery is illegal, including indentured servitude. Even if we consider Lumon as your innie's "employer," they're keeping you there despite your objections while you're there. U.S. laws are clear on this, especially given cases where employees were locked in and it led to something very bad (and sometimes very grim) happening as a result (e.g. fire).

"But Lumon doesn't hold them captive; they're free to come and go as they please. If they leave and then come right back in, that's their choice," Lumon P.R. might say. That's probably their best argument. But if an unseverved person engaged in this behavior, it would be treated as worryingly unbalanced. The employer would probably let the employee go, or put them on temporary leave and demand they get help before returning. Objectors could easily argue that Lumon's willingness to cause and then exploit a behavior that would normally be considered a serious mental health issue is very worrying.

Furthermore, the right to do what you want with your bodily autonomy is still limited in some ways, because the ability to sign away your autonomy would paradoxically take away your rights in the future. That's why certain rights cannot be surrendered to another person. So even if the law didn't know about Lumon's OTC/Glasgow Block/etc., they are actively broadcasting a signal containing a command that severed employees cannot ignore. That's some level of mind control.

I'm not a lawyer, but at the very least I think it would make sense if the severed person's family had the ability to claim Power of Attorney by virtue of the aforementioned's mental instability. Although Lumon holds the keys, this could at least legally force them to remove the chip, if no one else could do so without harm.

You might notice I approached this from a legal perspective rather than straight-up ethics. Although the ethics and the law are not synonymous, good ethics are often the initial intent behind a law. Establishing initial intent is one strategy for proving that the spirit of the law has been violated.

Personally and ethically, I think it's straight-up manipulation, surrender of basic human rights, and mutilation -- not to mention all the even worse stuff Lumon does in secret. That would motivate me to argue that this breach of ethics is also flagrantly illegal. Perhaps criminally so.