I know on building codes here you (even if you are fully competent to do so properly) are not allowed to work on anything yourself. You must pay someone to do it for you. If you go by the rules you are not even allowed to change out a basic light switch, install a new faucet on your sink, etc. It is sue happy world we live in now where everyone must be protected from themselves and government people need to justify keeping their jobs by coming up with more and more regulations. Also important to be aware of, the "trades" have to pay to get certified, the have to pay to take the exams, the certifications and exams are administered by those who get paid to write more regulations that become part of the exams, and they are also the very same ones who charge for the permits to do any sort of work, etc. So it is in their best interest in their own self preservation of their jobs to create even more regulations and rules because without all of that they would not have jobs.
That being said the general majority of people are totally incompetent in regards to anything electrical or mechanical and have no business whatsoever attempting anything more than changing a basic screw in light bulb. The regulations need to address in some way those who are totally competent at doing certain trades but have not paid for getting all of the certifications and permits.
What it comes down to is as others mentioned - your localities city hall will be the place to determine what is required where you are at.