I fully understand Nannawind why this gets your goat!
Airing it here is far, far better than commenting upon it to family, which you know, and don't do.
Sounds to me as if your DD's partner has a very large chip on his shoulder and boasts of all the things he can do (and perhaps some he can't) to impress.
As far as possible, let it go in the one ear and out the other.
If he is actually doing electrical work in the home that it is illegal to do unless one is a qualified electrician, driving without a licence or treating people without the proper medical qualifications, then he is breaking the law.
However, if you try to take the matter up with him, it will lead to one almighty family row, as like as not. If he is just saying he can do all these things better than those who have studied the subjects, then it's annoying, but try just to change the subject when he starts.