That's just a chain of trust. Who checks their surgeon's credentials before going under the knife? You trust the surgeon's employer and the medical registration

That's just a chain of trust. Who checks their surgeon's credentials before going under the knife? You trust the surgeon's employer and the medical registration board in your jurisdiction. The field of engineering offers a rough analog. In Australia there's a society called Engineers Australia, who via the ITEE, evaluate and accredit educational programs before accepting graduates of said programs as members. There are equivalent organisations around the world (just as there are in the fields of law and medicine). I can also give an example of how it works. My Bachelor of Information Technology states that I majored in Software Engineering. However the degree isn't accredited and therefore I'm not eligible for EA membership. I still refer to myself as a "software engineer" and show a degree from a reputable university, but I can't (and wouldn't) try pass myself off as an accredited Engineer.