Since you can exit, it's different. Generally countries enter various nominally binding arrangements all the time, like ratifying UN treaties that are consider

Since you can exit, it's different. Generally countries enter various nominally binding arrangements all the time, like ratifying UN treaties that are considered by courts to be part of national legislation etc. So "full sovereignty" in this sense is not so common. (Also, EU law is drafted via a representational democracy system, so this use of power has an important quality of legitimacy that law handed down from the empire would lack)