I'm not 100% certain but I'm about 99% certain that there is no such legal requirement. In part this is because in a very recent post I read about a particular CD offer, Ken Tumin specifically mentioned the lack of a grace period - https://www.depositaccounts.com/banks/frontwave-credit-union/offers/
Answers
(1) Automatically Renewable Time Accounts
This account will automatically renew at maturity.
You will have [_______ calendar/business] days after the maturity date to withdraw funds without penalty;
or
There is no grace period following the maturity of this account to withdraw funds without penalty.
Reference: https://www.fdic.gov/regulations/laws/rules/6500-3980.html
But there is no reason to worry if you simply set the CD up to automatically close to your savings or checking account. That way it can't rollover by accident and get locked in. The only advantage of a grace period is if you actually do want to renew it, but fail to act until after the maturity date. In that case, you would get interest during the grace period, but few places give the CD level interest, rather than the savings interest, if you close during the grace period.
I long ago started to always set CDs up at time of opening to close to my checking account at maturity. And closing to the checking makes it easy to move the money elsewhere buy simply writing a check. But I can still renew the CD if I want to.
The problem, as QED already pointed out, is that many will not let you set that up until very close to the end date.