State-Specific Laws: Each US state has distinct laws governing powers of attorney and authorization letters. Requirements for validity vary by state, including potential needs for notarization or witnesses.

Uniform Power of Attorney Act (UPOAA): A model law adopted by many states that provides standardized rules for creating and using powers of attorney, including scope and limitations of authority.

Federal Privacy Laws: Federal regulations including privacy protections, particularly relevant when handling medical information (HIPAA) or financial documents.

Principal Capacity Requirements: Legal requirements ensuring the person giving authority (principal) has the mental capacity to understand and grant the authorization.

Party Identification Requirements: Legal necessity for clear and complete identification of all parties involved in the authorization, including both the principal and the authorized agent.

Scope Definition Requirements: Legal requirement to clearly specify the exact powers and limitations being granted to the authorized agent.

Duration Specifications: Legal requirement to specify the time period for which the authorization is valid, including start and end dates if applicable.

Documentation Requirements: Physical document requirements including written format, original signatures, proper notarization, and witness signatures as required by state law.

Durability Provisions: Specifications regarding whether the authorization continues if the principal becomes incapacitated, known as a 'durable' power of attorney.