Restrictive covenants are often perfectly reasonable (where extensive training has been given or the employee has been made privy to trade secrets for example) which is why most countries permit them, so a blanket ban would not be wise.
There has been a blanket ban in California since 1872 and it has worked out very well for California. The classic example of this is that had they been bound by non-compete clauses, the "traitorous eight" would not have been able to leave Shockley Semiconductor in 1957 to found Fairchild Semiconductor. Without Fairchild, Silicon Valley would not exist, as Fairchild employees in turn started their own ventures (also not being bound by contractual agreements restricting them from work) as they came up with innovative new ideas.
