Should be the standard anyway. Reading email and texts from work, or responding to calls, is work. Unless your contact specifies on-call hours, you should ignore your boss outside of working hours. If they really want you to respond they can pay you overtime.
Places that specify on call time also tell you not to check stuff when you're not at work or supposed to be on call though, because that's expensive for them. And if they tell you to check something they just put you into on call pay.