The point being, that as head of the LN, if I see any bounty hunters trying to enforce liberty law, I will shoot them until they explode for vigilanteism. Unaccountable 'men-of-the-law' running around and dishing out justice as they see fit? Bad thing to have.
So, SeaEagle/SeaFalcon, you'd better stop with trying to enforce liberty law.
The blanket bounties are to deal with low profile criminals the lawful forces neither have the will nor the time or manpower to sort out. The bounty hunters are an ideal group dealing with that.