An alternative to banning them outright would be to mandate that the employee is compensated at something like 80%+ of annual pay for the agreement's duration for it to remain valid. So if McDonald's thinks their burger technology is that valuable they can pay to keep it under wraps for a while.
That is an interesting idea, but I can guarantee employers would fine ways around that very quickly. For example, maybe the law stipulates that employees must be compensated for 80% of salary, so employers start paying mostly in benefits and equity. Or we specify 80% of total compensation, and they find a way to say healthcare is worth nothing and grossly underestimate the initial value of equity. There's always a way. Banning it outright doesn't even guarantee it will work, because cartels will agree not to hire each other's recently departed employees.
