How could Ned have forbidden other nobles from having men under arms? Wouldn't they have seen it as the prelude of a purge?
Other nobles in the capital and at court. Since it's the King's court and the King's capital, he gets to make the rules for what's allowable conduct. And the Hand speaks with the King's voice.
Plenty of historical examples of late medieval Kings regulating how many men a lord could have in their retinues or wearing their livery (this was a major reform effort of Edward IV to restore the king's peace during the Wars of the Roses, and carried on by Henry VII), or regulating whether noblemen could carry weapons in the King's presence at court or could duel each other within the boundaries of the King's court.









