National Security Readiness Act of 2003

National Security Readiness Act of 2003 - Amends the Endangered Species Act of 1973 (ESA) to prohibit the Secretary of the Interior (or the Secretary of Commerce, as appropriate) from designating as critical habitat any land or geographical area controlled by the Department of Defense, or designated for its use, that is subject to an integrated natural resources management plan for a military installation under the Sikes Act, if the Secretary determines that the plan addresses special management considerations or protections.

Amends the Marine Mammal Protection Act of 1972 (MMPA) to redefine the term "harassment" as it relates to marine mammals to limit the meaning of: (1) any act that has the potential to injure a marine mammal or marine mammal stock in the wild to any act that has the significant potential to cause such an injury; and (2) any act that disturbs or is likely to disturb a marine mammal or marine mammal stock in the wild by causing a disruption of natural behavioral patterns to causing such a disruption to the point where such behavioral patterns are abandoned or significantly altered.

Authorizes the Secretary of Defense, after conferring with the Secretary of Commerce or the Secretary of the Interior (as appropriate), to exempt any action undertaken by the Department of Defense from requirements of the MMPA, if the Secretary of Defense determines that the action is necessary for national defense. Limits such exemption to a renewable two-year period.

Repeals the limitation to a specified geographical region or a region of small numbers of any allowance of incidental, but not intentional, taking of marine mammals by U.S. citizens engaged in a specified activity (including a military readiness activity) other than commercial fishing.

Exempts the Secretary of the Interior (or, as appropriate, the Secretary of the department in which the National Oceanic and Atmospheric Administration is operating) from the requirement to publish notice (except in the Federal Register) with respect to incidental takings of marine mammals and marine mammal products while engaged in military readiness activities authorized by the Secretary of Defense. (Currently, the appropriate Secretary is required to publish notice also in newspapers of general circulation, and through electronic media, in the coastal areas that may be affected.)

Limits the Department of Defense responsibility under ESA for water consumption impacts on critical habitats or endangered species to: (1) water consumption occurring on a military installation, whether the source of the water consumed is located on or off the installation; or (2) water consumption occurring off of a military installation and the source of the water is under the direct control of the Department of Defense. (Exempts military installations from certain ESA requirements regarding official actions or agency actions with respect to civilian water consumption impacts on critical habitats or endangered species.) States that nothing shall prohibit a military installation from voluntarily undertaking efforts to mitigate water use and consumption.