In the event of the death a present or former official of the government of any State, territory, or possession of the United States, the Governor of that state, territory, or possession may proclaim that the National flag shall be flown at halfstaff.

Why is the flag at Half Staff? Flag Honors for State of Michigan

For more information on flying the American Flag at Half Staff:

Presidential Proclamations which include half staff orders:

Celebrating America’s Freedoms: United States Department of Veterans Affairs

United States Flag Code