What justifies granting lawyers a monopoly over the representation of others before a court?

Answer 1

There are instances in which a person may represent themselves before a court. However, to answer your question directly, a couple of reasons that only those who are licensed to practice certain professions are permitted to actually practice those professions are to insure the quality of service provided, and to allow the profession to regulate itself. For example, would you want someone who wasn't actually a licensed physician to operate on you? Would you want someone who wasn't an engineer to build the overpass you drive under on a daily basis? Would you want someone who wasn't an architect to design your home? Would you want someone who wasn't a CPA to do your taxes? Would you want someone who wasn't a law enforcement officer patrolling your neighborhood while carrying a gun and handcuffs with the authority to arrest persons, yourself included? Would you want someone who didn't have a commercial driver's license driving an eighteen wheeled tanker truck full of gasoline around your neighborhood?