Beyond that it said a letter of refrence from a "Command level officer" is needed.
What, for the sake of refrence, is a command level officer.
Someone commander and above, a Redshirt?
A command level officer would be someone qualified for command. Specifics of experience aren't known. For instance, could Riker or Data write a letter of reference? Apparently Sisko, as the highest ranking officer in the Bajor system, was the local go-to guy for these letters. But that doesn't tell us much.
Ideas how most people find a command level officer to sponsor them, or is the policy MEANT to exclude those not allready chummy with such a individual.
Like say Ro Larren probaly didnt meet a starfleet officer till she fled her homeworld.
I doubt it was meant to exclude people. I'm sure one could contact Starfleet and discuss joining the service without having to be best friends with a command-level officer's son.