It was because of the 'Over Reaction' by the National Guard that the decision was made not to supply (or limit) live ammo to the Airborne Units.
Here is a little more of what I found about the addition of the 82nd and 101st:
By late Sunday, looting had reached Mack Avenue on the East Side, roughly five miles from where it had started, moving Gov. George Romney to call in 400 state troopers and activate the Michigan National Guard. West of Woodward Avenue, from Highland Park to the Detroit River, 8,000 Guardsmen accompanied first responders and patrolled areas of turmoil. Though trained in handling weapons, they were unequipped to deal with urban conflict. The mostly white Guard overreacted to intense situations on the West Side, which led to needless casualties and death.
The intervention of the State Police and National Guard, as well as a curfew instituted between 9:00 p.m. and 5:30 a.m., were not enough to prevent the situation from escalating. On Monday, July 24, Gov. Romney requested federal troops, and soon members of the 82nd and 101st Airborne Divisions were stationed around Detroit’s East Side. Many of the men were familiar with intense combat situations from active duty in Vietnam. The fact that the East Side came under control much sooner than the West Side has been attributed to the soldiers’ experience in the field, their racial integration, and their lack of live ammunition.
As tanks rolled through the city and widespread food shortages took their toll, the chaos began to dissipate. Sniper fights, fires, and small outbursts of violence continued sporadically until July 27, when the conflict officially ended.
The End