Order won't spontaneously arise. It must be maintained. The opposite of order is chaos.
And too much order is tyranny. Both ends mean excesses in violence, so the middle is to be sought.
A few plainclothes security officers do not an army make.
...But a Galaxy
class starship for the UFP President is plenty enough to meet the criterion.
I wonder whether the UFP President really has Men in Black around him or her? It would be a rather nifty alternative to simply have him or her wear a forcefield belt, somewhat more potent than the TAS ones that couldn't stop phasers; random rioters couldn't touch the Prez, but the protection wouldn't be excessive or call for escalation. Essentially, it would be an invisible armored limo, a soft tool for good PR and adequate protection. (MIB to catch the fool who nevertheless takes a shot at the Prez would be optional. Regular law enforcement ought to be up to the task in the Trek environment...)