Our accreditating agency insists that that faculty members have got a degree (actually 18 credit hours at graduate level) in the subject they teach. If you are a foreigner it's a pain in the arse, because you need to produce an equivalency evaluation, even more so when your degree wasn't modular.
It causes complications when you teach an allied subject (say your degree certificate says you are a physicist and teach physical chemistry in the chemistry department) but it's easy to see why the accreditator insists: there was a time when there were too many unqualified people teaching.
The real trouble occurs when the institution mistakes certification for qualification, but that's a different story.
If a school won't comply to licensing requirements they government will levy a fine. If a school fails accreditation students will run away, they rightly think that employers won't take their degree seriously. There also won't be federal student loans.
Sometimes professional bodies approve degrees. There are no consequences at all, except that the more capable students stay away from unrecognized degree programs. At my department they are actually moving away from adjuncts because the professional body requires that courses be taught by full-time lecturers or professors. Leadership has decided that the extra expenses for full-time faculty members with benefits are justified by the improved quality of students.
Five weeks is not enough prep for most teachers. I know many awesome teachers for whom it worked out very well. For me, it didn't. But Teach For America is extremely selective in trying to identify people who will be successful with minimal training. That's what it takes to roughly match the performance of traditionally trained teachers. I don't think we need lower barriers to entry, especially without a similar level of accountability.