Again, not a lawyer, I know fuck all about International law, but it sure does look like boobytrapping random people's electronics is a fucking crime.
Article 3, part 8 (b) and (c) are the most clearly breached sections:
8.The indiscriminate use of weapons to which this Article applies is prohibited. Indiscriminate use is any placement of such weapons:
(a) which is not on, or directed against, a military objective. In case of doubt as to whether an object which is normally dedicated to civilian purposes, such as a place of worship, a house or other dwelling or a school, is being used to make an effective contribution to military action, it shall be presumed not to be so used; or
(b) which employs a method or means of delivery which cannot be directed at a specific military objective; or
(c) which may be expected to cause incidental loss of civilian life, injury to civilians, damage to civilian objects, or a combination thereof, which would be excessive in relation to the concrete and direct military advantage anticipated.