Yes, if it's accessible, and nothing implies that you shouldn't - why not?
If a cable is not meant to be unplugged - there should either be a warning sign/message, a protection measure (even a nominal one, serving as a mere warning), or you shouldn't normally get access to it in a first place.
Obviously, there is common sense, too - you don't plug some working medical equipment, even though there may be no warnings - it's implied that it's commonly understood that disconnection would interfere with device's operation and endanger the patient. Or you don't suddenly turn off someone's PC at office just because the power outlet isn't covered by the table.
The door example is also misleading and plain wrong analogy. We're not talking about trespassing on others' property. When you rent a room, it's a common sense that you shouldn't steal the TV from it, but nothing tells you if some random Ethernet cable is some private network or just a WiFi replacement. It's the same as any other electrical socket (well, except it's a plug, not socket) - nothing implies that you can't use it, as long as you don't cause any damage to the property. If a rented room has a floor fan plugged in, I doubt you shouldn't be allowed to plug it out or even satisfy your curiosity and measure how much power it consumes. As long as you don't damage anything, of course.
There are too many people out there who want to plug in some odd lawmaking solutions (always, restrictions) that don't actually solve anything.
If a cable is not meant to be unplugged - there should either be a warning sign/message, a protection measure (even a nominal one, serving as a mere warning), or you shouldn't normally get access to it in a first place.
Obviously, there is common sense, too - you don't plug some working medical equipment, even though there may be no warnings - it's implied that it's commonly understood that disconnection would interfere with device's operation and endanger the patient. Or you don't suddenly turn off someone's PC at office just because the power outlet isn't covered by the table.
The door example is also misleading and plain wrong analogy. We're not talking about trespassing on others' property. When you rent a room, it's a common sense that you shouldn't steal the TV from it, but nothing tells you if some random Ethernet cable is some private network or just a WiFi replacement. It's the same as any other electrical socket (well, except it's a plug, not socket) - nothing implies that you can't use it, as long as you don't cause any damage to the property. If a rented room has a floor fan plugged in, I doubt you shouldn't be allowed to plug it out or even satisfy your curiosity and measure how much power it consumes. As long as you don't damage anything, of course.
There are too many people out there who want to plug in some odd lawmaking solutions (always, restrictions) that don't actually solve anything.