Parents can disallow all kinds of things that either aren't addressed or prohibited by law. For example, parents can set a curfew, bedtime, insist homework be done before hanging out with friends, forbid a teenager from getting a driver's license, ground them, forbid them from using the phone/computer/social media, etc. Parents can also forbid someone to have contact with their child, or put limits on when and how that contact occurs. About the only exception is the law does give those under 18 the right to some forms of medical treatment without parental consent, and even that varies a lot by state and circumstance.