Guaranteeing a United and Resolute Defense Act of 2003

Guaranteeing a United and Resolute Defense Act of 2003 - Authorizes the Secretary of Defense to provide funds to the governor of a State who submits, and receives approval of, a plan for the use of personnel and equipment of the State's National Guard in homeland security activities. Provides authorized uses of such funding, including: (1) pay, allowances, and clothing; (2) equipment and facilities operation and maintenance; and (3) procurement of related services. Authorizes State National Guard personnel to perform full-time National Guard duty to carry out homeland security activities under a State plan.

Allows a current State drug interdiction and counter-drug activities plan to be included as an annex to a State's homeland security activities plan.

Authorizes National Guard personnel, while on orders to support counter-drug activities, to participate in additional military training to promote military readiness, including attendance at schools.