A Level D Alert Warning (レベルディー警戒警報 Reberu Dī Keikai Keihō), commonly abbreviated as a Lv.D Alert Warning, is an official alert that can be issued by the World Void Information Controlling Organization.
One of several alert warnings that the Controlling Organization can officially give; Level D indicates that no other person belonging to any official organizations can enter the designated area that is under the alert warning. The designated areas are ones controlled by the Controlling Organization, which means that all Hierarchical Cities can be put under this arrest. The only time this is shown is in BlazBlue: Calamity Trigger and BlazBlue: Continuum Shift within the 13th Hierarchical City "Kagutsuchi".
In BlazBlue: Calamity Trigger, the Controlling Organization declares Kagutsuchi under Level D status when Jin Kisaragi went AWOL and was suspected to be lurking inside the city due to the recent appearance of Ragna the Bloodedge. When Hazama and Noel Vermillion arrived inside the city to try and apprehend Jin, Hazama warned Noel about the Alert Warning.
Seventh Agency repeatedly breach this official alert due to sending both TR-0009 Tager and Lambda-11 down to Kagutsuchi. In BlazBlue: Calamity Trigger, Noel encounters Tager, gives him an official warning about the status of Kagutsuchi and then orders him to evacuate the vicinity; after Tager refuses to do so, the two engage in combat only for the consequent outcome to become unknown.
After the events of both BlazBlue: Calamity Trigger and BlazBlue: Continuum Shift, it is unknown if Kagutsuchi is still under the warning or not.