These are the laws for the states with most population in the United States.

Alabama
- No one under the age of 21 is allowed to purchase, consume, possess, or to transport any alcohol.

Arizona
- No one under the age of 21 is allowed to purchase or possess alcohol. Although in the performance of a religious service or ceremony, possession or consumption of alcohol is allowed. The BAC for someone at least 21 years old or older is a BAC of 0.08 or higher.

  Arkansas
- No one under the age of 21 is allowed to consume or posses alcohol. Anyone under the age of 21 can't drive any motor vehicle with a BAC of .02 but less than a BAC of .10. For anyone 21 years of age or more the BAC limit is .10 or higher.

  California
- No one under the age of 21 is allowed to consume or possess alcohol. It's illegal to drive a motor vehicle with a BAC of .01 or more if under the age of 21. For anyone 21 years of age or older may not drive if they have a BAC of .08 or higher.
 
  Colorado
- No one under the age of 21 is allowed to consume or possess alcohol unless a parent or guardian gives permission for their child or ward to drink, but only on private property and under the supervision of the parent or guardian. Anyone under the age of 21 can't drive any motor vehicle with a BAC of .02 but less than a BAC of .05. Anyone 21 years of age or older may not drive if they have a BAC of .10 or higher.
 
  Connecticut
- A minor can't drink alcohol,  but someone 21 years old or older is .10.  

  Idaho
- No one under the age of 21 is allowed to consume, or possess alcohol. Someone under the age of 21 can not drive any motor vehicle with a BAC of .02 but less than a BAC of .08. The BAC for anyone over 21 years of age or older is a BAC of .04 but less than a BAC of .08.

 Indiana
- No one under the age of 21 years is allowed to consume, transport, or possess alcohol. But he/she is allowed to consume, transport, or posses alcohol when supervised by the parent or guardian. Something also interesting, no one under the age of 18 is allowed in tavern, bar, or other public place where alcoholic beverages are sold, bartered, exchanged, given away, provided, or furnished. But is allowed when the child is with a parent, guardian, trustee, or other family members.

  Iowa
- No one under the age of 21 is allowed to consume or posses alcohol, unless at a private home when the parent or guardian gives it to his/her child or ward and the said parent or guardian is present. Also anyone under the age of 21 can not drive any motor vehicle with a BAC of .02 or higher. For anyone 21 years of age or older may not drive if they have a BAC of .10 or higher.  

  Maryland
- No one under the age of 21 is allowed to buy, consume, posses, or transport alcohol. But to transport alcohol for any lawful purpose with the consent of the parent or guardian is allowed.  

  Missouri
- No one under the age of 21 is allowed to purchase alcohol.  

  New York
- No one under the age of 21 is allowed to buy or posses alcohol. But you can drink alcohol if you are a student in a curriculum licensed or registered by the state education department and is required to taste or imbibe alcoholic beverages in courses which are part of the required curriculum. Also you can consume alcohol if it is give to you by your guardian or parent. I didn't find the BAC limit for anyone under 21, the BAC is .10. After November 1, 2003 the new law is .08.  

  Ohio
- No one under the age of 21 is allowed to possess or consume any alcohol in any public or private place, unless the underage person is accompanied by a parent, spouse who is not an underage person, or legal guardian. Also anyone under the age of 18 is not allowed to possess or consume any low-alcohol beverage in any public or private place, unless accompanied by a parent, spouse who is not an underage person, or legal guardian. The limit of intoxication to drive a vehicle for someone under 21 years of age is a concentration of at least two-hundredths of one gram but less than ten-hundredths of one gram by weight of alcohol per two hundred ten liters of the person's breath. For everyone 21 years of age or more it's concentration of ten-hundredths of one per cent or more but less than seventeen-hundredths of one per cent by weight of alcohol in the person's blood.

  Rhode Island
- No one under the age of 21 is allowed to buy or posses alcohol. The BAC for someone at least 21 years old or older is more than a BAC of 0.08 but less than 0.10.

  South Carolina
- No one under the age of 21 is allowed to buy alcohol. But a college student who is 18 years or old can taste, but not consume or imbibe the liquor required for curriculum and is used only for instructional purposes during classes. There are many different ways to be charged with drinking under the influence (DUI).

  Tennessee
- No one under the age of 21 is allowed to purchase, transport, or possess alcohol. Anyone under the age of 21 can not drive any motor vehicle with a BAC of .02 or higher. For anyone 21 years of age or older can not drive if they have a BAC of .08 but less than a BAC of .10.

  Texas
- No one under the age of 21 is allowed to purchase, posses, or consume alcohol. Possession and consumption of alcohol is legal for minors if under the supervision of a parent, guardian or spouse. Anyone under the age of 21 can not drive a motor vehicle with any traceable amounts of alcohol in the blood stream.

  Utah
- No one under the age of 21 is allowed to purchase, possess, or consume alcohol. The BAC for someone at least 21 years old or older is a BAC of 0.08 or higher.

  Virginia
- No one under the age of 21 is allowed to purchase or possess alcohol. For anyone 21 years old or older the BAC is 0.08 or more.

  Washington
- No one under the age of 21 is allowed to purchase alcohol . Anyone under the age of 21 can not drive any motor vehicle with a BAC of .02 or higher. For people 21 years of age or older, they can not drive if they have a BAC of .08 or higher.

 West Virginia
- No one under the age of 21 is allowed to purchase or consume alcohol.