Which of the following substances is NOT associated with significant legal restrictions?

Caffeine is a substance that is widely consumed and generally considered safe for most people when used in moderation. It is not associated with significant legal restrictions, in contrast to other options provided. PCP (phencyclidine), oxycodone, and crack cocaine are all controlled substances that fall under varying degrees of regulation due to their potential for abuse, addiction, and serious health impacts.

PCP is a dissociative anesthetic that is classified as a Schedule II drug, indicating a high potential for abuse and limited medical use. Oxycodone, an opioid pain medication, is also highly regulated due to its addictive properties and the opioid crisis. Crack cocaine, a powerful stimulant, is classified as a Schedule II drug as well and is subject to severe legal penalties due to its association with addiction and criminal activity. Consequently, caffeine's legal status as a commonly consumed beverage distinguishes it clearly from these other substances.