Anyone can do this while mounted if they have the appropriate skills.
Plus, there is a fairly obvious way of stopping someone running away in fear, tho you cannot give it with poisons unfortunately. Other than that, I know of no way of stopping flight.
However, since you have the ability to track people around the place, fire arrows off into the distance, and throw stuff at people, a knight fleeing on low health should be an easy target, no?
Written by my hand on the 17th of Skyelong, in the year 1032.