What other things are you prohibited from doing in letters- besides drinking?

[TSteven]

Legal Drinking Age

exert

While it is commonly believed that the minimum drinking age is 21, people can legally drink below that age under many different circumstances.

The National Minimum Drinking Age Act of 1984 required all states to raise their minimum purchase and public possession of alcohol age to 21. States that did not comply faced a reduction in highway funds under the Federal Highway Aid Act.... It does not prohibit persons under 21 (also called youth or minors) from drinking. The term "public possession" is strictly defined and does not apply to possession for the following:

~ An established religious purpose, when accompanied by a parent, spouse or legal guardian age 21 or older
~ Medical purposes when prescribed or administered by a licensed physician, pharmacist, dentist, nurse, hospital or medical institution
~ In private clubs or establishments
~ In the course of lawful employment by a duly licensed manufacturer, wholesaler or retailer.”

Many of the states that have chosen to specifically prohibit alcohol consumption by those under age 21 have a variety of exceptions. For example,

Some States allow an exception for consumption when a family member consents and/or is present. States vary widely in terms of which relatives may consent or must be present for this exception to apply and in what circumstances the exception applies. Sometimes a reference is made simply to "family" or "family member" without further elaboration.

....

Some States allow an exception for consumption on private property. States vary in the extent of the private property exception which may extend to all private locations, private residences only, or in the home of a parent or guardian only. In some jurisdictions, the location exception is conditional on the presence and/or consent of the parent, legal guardian, or legal-age spouse.

Some States also allow exceptions for educational purposes (e.g., students in culinary schools), religious purposes (e.g., sacramental use of alcoholic beverages), or medical purposes.

Edited to add disclaimer from link

Laws are constantly changing and efforts are made to provide accurate and current information. However, this information cannot be guaranteed as to accuracy, is not intended as legal opinion or advice, and is not a substitute for the services of an attorney. Those in need of information about the application of law to their circumstances are encouraged to consult a qualified lawyer.