The answer to this question is chillingly presented to the reader in the figure of Mr. Taber and what Bromden remembers happened to him when he refused to take his medication. In fact, all Taber did was refuse to take the medication without being told what it was, but this was interpreted as a refusal by Nurse Ratched. As he, according to her, refused to take his medication "orally," he was forcibly mahandled and give him an injection in his rear:
They push him face down on the mattress. One sits on his head, and the other rips his pants open in back and peels the cloth until Taber's peach-colored rear is framed by the ragged lettuce-green... The nurse comes down the hall, smearing Vaseline on a long needle, plls the door shut so they're out of sight for a second, then comes right back out, wiping the needle on a shred of Taber's pants.
Such horrendous abuse clearly signals the way that the inmate's rights are taken away from them and how they are abused if they do not conform to Nurse Ratched's strict rule. Kesey uses the treatment of patients in this novel to question the way that such behaviour is justified through the use of labeling by society. If you label somebody as being mentally unwell, or "mad," suddenly they seem to lose all basic human rights. The novel suggests this is profoundly wrong.