Probably. My previous contract had this, and I've had CEO e-mail coming in to me personally with nicely worded threats once he found out where I got employed the day after quit. The company was multinational, I just rechecked the issue with legal experts here and decided against sending "now how would you like to suck my balls" reply because as far as I should be concerned, I don't know what he's talking about. All the things I've signed in the contract do not carry any weight because they are outside the framework of labor laws. There are exact and structured pieces of information that are legally binding in the contract, like hours and pay, all rest is bogus.
So, no reply and no issue.
Btw. same thing with EULA in EU, those stupid texts software makes you scroll down and "agree" to. Essentially the only legally binding EULA constructs will be those perfectly aligned with the consumer laws and regulations. As with work contracts you'll be looking for just one or two things there - like permission to use inside business, everything else is garbage.