[deckeraa]

You would use the various methods for determining competence used in other less-regulated fields, such as degrees, certification, and word-of-mouth. The major difference would be that individuals could choose how they wished to determine which doctors they wished to use[1].

To give an example, many people who wish to become doctors are required to go through a residency program that features elements such as required 24 hours shifts. Personally, I would be quite fine seeing a doctor who wasn't required to do such shenanigans. As it stands right now, I can't make that choice, because various special interest groups have gained a government-granted monopoly on the certification of physicians.

[1] One objection would be that, if we didn't have the force of law (which is the force of violence) keeping "quacks" from practising medicine, then many people, particularly the poor, would actually have /less/ choice. This is a utilitarian argument, but even if the premise of utilitarianism is granted, this still seems incorrect due to two factors. First, regulatory capture has led to a system that already can prevent poor people from accessing care. No care is probably worse that mediocre care. Second, the U.S. (as a nation) spend more money than other developed nations on healthcare and gets similar outcomes. This seems to indicate that a lower cost of care wouldn't necessarily cause a sudden influx of quacks onto the market.