Very rarely, if ever.
The only time it is justifiable is if it's either pre-agreed or if there is a threat to the child.
If there is reason to think they are being groomed, or used in some way, then yes. E.g. a room search after getting information that they are holding drugs for a dealer. They should be treated like a police search. Only done when there is real reason, rather than just fishing.
If it's pre-agreed that a device isn't private, then the rules change slightly. A younger child's phone or computer should be subject to respectful monitoring. It should also be part of an open and equitable discussion on boundaries and rules. Even here, the goal should be to protect the child from dangers, not to snoop on what they are chatting with friends about beyond that.
Privacy, is an important thing for children. It needs to be provided with guard rails initially, but should be respected as best you can.
There's an interesting argument that honey can be vegan, by that criteria.
A bee colony is not generally trapped in a hive. They are capable of leaving, if it's not to their standards, or they find somewhere between. The catch is that artificial bee hives are amazing for bees, compared to natural locations. The only catch is the "rent" taken by the eldritch creatures. They never take too much however, only taking excess the hive doesn't need.
Basically bees could be argued to be paying rent, in honey, for high quality accommodation.