The author's underlying premise is that the legal profession has a high barrier to entry that, in turn, guarantees high salaries.
Each step is a filter. For example, only 66% of students finish high school. Fewer complete a university degree. Even fewer are admitted to law school, and even fewer complete it. 30% of law school graduates are going to fail the bar exam, and only about 10% of these students will land a job at a good law firm. Finally, only about 20% new associates in a good law firm are likely to make partner.
As a result, very competent people who could certainly serve as excellent lawyers are barred from giving legal advice to anyone (for example, Bill Gates, Richard Branson, Michael Dell, and Rush Limbaugh). Also, the legal bar has an adverse effect on minorities, limiting the number of minorities available to serve as potential judges and legal advocates. But, these restrictions to practice keep legal fees at a healthy $300 per hour.
It is important to recognize the point he makes in the second paragraph above: while proving to be an effective barrier to entry, these filters largely test a person's work ethic and commitment, not their intelligence. Sure, you have to be reasonably intelligent to get through law school and pass the bar, but there is a reason the legal profession attracts the super Type A personalities. As someone who is both a part-time law student and a software engineer, I've encountered many more people I would consider "brilliant" in the technical world than in the legal world.
I think the legal profession is the "now what?" choice for a lot of people. Many (not all, of course) end up there because they don't know what else to do and, unlike many other advanced degrees, doesn't require a specific background.
If you want to go to medical school, there's a rigid program that you take the minute you enter college. And if you happen to party to o much during your freshman year and bomb Bio, well, you might as well change majors immediately. Similarly, pursuing a Ph.D. in mathematics or computer science or economics would be very difficult without the relevant background.
Law school doesn't have such prerequisites. In that sense, the barrier to entry is lower. Anyone, regardless of your background, can go to and be successful in law school. There are no subject tests on the LSAT.
Of course, the point he's making is that there are no barriers to entry for a software developer. He may be right in terms of formal barriers, but I have to disagree that "anyone" can be a software developer. Like many of you, I started programming at a young age. I probably learned as much through experimentation and developing on my own than I did in my formal education. Creativity, technical knowledge, and problem-solving are all critical to being a software engineer.
By contrast, the nature of the law is following precedent. Generally, I would say there is little "innovation" (by design) and, in many aspects, originality and creativity is frowned upon.
I was actually discussing this with my girlfriend the other day. Lawyers really have a great racket going. Their higher salaries are a direct result of an artificially limited supply and speak nothing about quality. Then again, developers will generally make a very nice living without working 100 hour weeks or shelling out $100k for a degree.
Maybe the software engineers aren't stupid after all.