Military Construction Authorization Act for Fiscal Year 2003 - Title XXI(sic): Army - Authorizes the Secretary of the Army to acquire real property and carry out military construction projects in specified amounts at specified installations and locations. Authorizes such Secretary to construct or acquire family housing units, carry out architectural planning and design activities, and improve existing military family housing in specified amounts. Authorizes appropriations to the Army for fiscal years after 2002 for military construction, land acquisition, and military family housing functions of the Army. Limits the total cost of construction projects authorized by this title.(Sec. 2105) Amends certain prior military construction authorization Acts to increase the amounts authorized for chemical demilitarization projects at: (1) Forts Carson and Jackson in Colorado; (2) the Blue Grass Army Depot, Kentucky; (3) the Newport Army Depot, Indiana; and (4) the Pueblo Chemical Activity, Colorado.Title XXI: Navy - Provides, with respect to the Navy, authorizations paralleling those provided for the Army under the previous title.(Sec. 2205) Amends the Military Construction Authorization Act for Fiscal Year 2002 to: (1) increase the amount authorized for a construction project at the Naval Station, Norfolk, Virginia; and (2) revise the number of certain military housing units at Quantico, Virginia.Title XXIII: Air Force - Provides, with respect to the Air Force, authorizations paralleling those provided for the Army under Title XXI.Title XXIV: Defense Agencies - Authorizes the Secretary of Defense (Secretary) to acquire real property and carry out military construction projects in specified amounts at specified installations and locations. Authorizes the Secretary to carry out certain energy conservation projects. Authorizes appropriations to DOD for fiscal years after 2002 for military construction, land acquisition, and military family housing functions of the Department of Defense (DOD). Limits the total cost of construction projects authorized by this title.Title XXV: North Atlantic Treaty Organization Security Investment Program - Authorizes the Secretary to make contributions for the North Atlantic Treaty Organization (NATO) Security Investment Program and authorizes appropriations for fiscal years after 2002 for such Program.Title XXVI: Guard and Reserve Forces Facilities - Authorizes appropriations for fiscal years after 2002 for acquisition, architectural and engineering services, and construction of facilities.Title XXVII: Expiration and Extension of Authorizations - Terminates all authorizations contained in Titles XXI through XXVI of this Act on October 1, 2005, or the date of enactment of an Act authorizing funds for military construction for FY 2006, whichever is later, with exceptions. Extends certain prior-year military construction projects.Title XXVIII: General Provisions - Subtitle A: Military Construction Program and Military Family Housing Changes - Authorizes the Secretary of the Army to lease additional family housing units in Korea both at and above the current lease limit of $25,000 per year (to a maximum of $35,000 per year).(Sec. 2802) Amends the Military Construction Authorization Act, 1984 to repeal U.S. source requirements for military family housing construction overseas.Subtitle B: Real Property and Facilities Administration - Authorizes the Secretary or the Secretary of a military department to enter into agreements with private entities to address the use or development of real property in the vicinity of a military installation in order to: (1) limit any property development or use that is incompatible with the installation's mission; or (2) preserve habitat in a manner that is compatible with environmental requirements and current or anticipated military training, testing, or operations. Outlines agreement requirements and conditions. Provides agreement funding through funds of the Range Enhancement Initiative Fund of DOD.(Sec. 2812) Authorizes the Secretary concerned to convey to State or local governments or appropriate private entities surplus real property for the conservation of open space or natural resources. Provides a reversionary interest if the property is not used and maintained for such purposes.(Sec. 2813) Amends the Military Construction Authorization Act for Fiscal Year 2002 to authorize the Secretary or the Secretary of a military department (currently, only the Secretary of the Army) to conduct a demonstration program on the reduction of long-term facility maintenance costs. Allows up to 12 (currently three) contracts to contain requirements for such program. Provides transitional provisions for program contracts currently administered by the Secretary of the Army. Requires the Secretary to undertake current program report requirements.Provides funding from military construction funds defense-wide or of all the military departments (currently, only Army construction funds).Subtitle C: Land Conveyances - Authorizes the Secretary of the: (1) Army to convey to the State of Alaska or an Alaska Native Corporation or Indian tribe certain property formerly used for the Alaska National Guard; (2) Army to convey to the city of Hopkinsville, Kentucky, an abandoned railroad spur at Fort Campbell, Kentucky, for storm water management, recreation, transportation, and other public purposes; (3) Navy to convey to the city of Chicopee, Massachusetts, a portion of the Westover Air Reserve Base in Chicopee, for economic and other public purposes; (4) Navy to convey to the State of Rhode Island the Melville Marina site in Rhode Island; (5) Air Force to convey to the State of Colorado all or part of the Watkins Communications Site in Arapahoe County, Colorado, in exchange for certain lands adjacent to Buckley Air Force Base, Colorado; and (6) Interior to convey to the city of West Wendover, Nevada, and Tooele County, Utah, specified portions of the Wendover Air Force Base auxiliary field determined by the Secretary of the Air Force to be no longer required for Air Force purposes.(Sec. 2823) Amends the Military Construction Authorization Act for Fiscal Year 2002 to allow the transfer of the Corea and Winter Harbor properties as part of a conveyance to the State of Maine or political subdivision or tax-supported agency thereof. Exempts such conveyances from a Federal screening requirement.(Sec. 2827) Authorizes the Secretary to acquire all rights and interest to the Boundary Channel Drive Site, Arlington, Virginia, for inclusion in the Pentagon Reservation.Subtitle D: Other Matters - Authorizes the Secretary of the Air Force, using Air Force military construction funds, to transfer $15 million to the Secretary of the Interior in lieu of the acquisition of replacement property required after a transfer of certain lands within the Nevada National Wildlife Refuge System.