[voteNRA]

From MN statutes:

....... (2) person under the age of 21 years to consume any alcoholic beverages. If proven by a preponderance of the evidence, it is an affirmative defense to a violation of this clause that the defendant consumed the alcoholic beverage in the household of the defendant's parent or guardian and with the consent of the parent or guardian......

click the text for the actual statute

[svcw]

I misspoke some states do allow drinking when served by a parent.

Here is another link: http://www.youthrights.org/dastatelist.php

The link does have some state laws missing but its a start.