State Defense Force Improvement Act of 2003

State Defense Force Improvement Act of 2003 - Recognizes State defense forces as integral military components of the Nation's homeland security effort, while reaffirming that such forces remain entirely State regulated, organized, and equipped and recognizing that they will be used for homeland security purposes exclusively at the local level under State law.

Authorizes the Secretary of Defense to coordinate homeland security efforts with, and provide assistance (including the use of Department of Defense (DOD) property, equipment, and facilities) to, a State defense force, upon request. Makes participation by a State defense force in a DOD training program at the discretion of the State. Requires a State to reimburse DOD for training assistance costs. Makes the State liable for any injuries or damages incurred by a defense force member while engaged in training activities or State active duty.