Department of Defense installations will no longer accept driver's licenses from five states as proof of indentity for people trying to gain access.

The five states whose licenses are unacceptable are Minnesota, Illinois, Missouri, New Mexico and Washington, as well as American Samoa.

The ban is mandated by the REAL ID Act of 2005, which was enacted by Congress in response to the Seot 11, 2001, terror attacks on the United States. Some of the terrorists involved carried licensees from Virginia and Florida.

Under the act, driver's licenses must have specific security features to prevent tampering, counterfeiting or duplication. Licenses must also present data in a common, machine-readable format.

Exemptions to the rule were provided to give state governments time to comply with the federal requirements. Other exemptions are related to life or safety issues -- i.e. medical emergencies.

"Those attempting to gain physical access to DOD installations [with unapproved licenses] must show an alternate form of identification, such as a passport," DOD officials said. "Service members, family members, DOD employees, and federal employees with the DOD common access card, DOD uniformed services identification and privileges cards, federal personal identification verification cards or transportation workers' identification credentials are not affected," the Department of Defense said.

Jeh Johnson, secretary of the Department of Homeland Security, said the regulations will be enforced in October by the Transportation Security Administration on the traveling public at U.S. airports