IANAL but, as far as I know, e.g. here in Italy things work like this: assuming you decide to leave your day job to found your own company meant to compete with the company you were working for, your former employer could theoretically sue you if you found your new company within 5 years of you leaving (at least this is what I remember). To work around this, you could pick a partner and make them the head of the company. This could also work in spite of non-compete clauses, which I think many companies consider as overkill anyway.

As far as laws preventing your from moving from a company to a competing one go, I really don't think we have anything like that. Same goes with taking old employees with you if you move to another company. Which is a Good Thing, if you ask me, because if people decide to walk away it's probably because they are sick of it or found something better/better paying/more interesting, and law preventing you from moving someplace better would be preposterous, IMHO.

Of course, this "lack of regulation" might have to do with the fact that the vast majority of contracts are of the collective type and not tailored to your particular company, meaning that you work under the same conditions as most of the other people doing your job.

According to my limited experience, a company drafting up its own contracts is a rare occurrence.