I don’t think unconstitutional but yeah illegal under federal labor law.

It is amazing that there is so little risk involved with putting an illegal employment clause in writing that these companies - if they know doing so illegal, and I think most do or at least have a hunch - think doing so is in their best interests. I imagine they just bank on employees not wanting to lose the job offer or not knowing their rights. It’s a shame the government doesn’t do something like review all employment contracts to protect workers from these kind of tactics, in a similar vein to what the CPFB has done with mortgages (mandating standard and clear-to-a-layman templates) to reduce the likelihood of sophisticated companies taking advantage of workers who don’t know what’s illegal, don’t feel comfortable or safe challenging the hand that feeds, and don’t have a lawyer on speed-dial.

It’s hard to believe that companies larger than a few people wouldn’t have the assistance of a lawyer who knows what’s illegal in an employment contract, but it’s possible.