[Dannymetconan]

They work based on what someone is prepared to enforce and the laws of the country they try to enforce it in. Having it written and signed isn't some magic catch all.

I'm sure they can fire you but it seems to be "at will" employment in most of the US anyway.

In Ireland and Canada such a clause would likely fall under being "unreasonable" for low paid employees. Similar to how a "non-compete" is not worth the paper it's written on (excluding when direct financial compensation is paid. Eg gardening leave).