When arriving in some countries you must fill out an arrival form at customs and immigration. You may also be asked some questions by customs agents.
In some countries one question is whether or not you packed your own bags.
- Must everybody always answer "yes" to this question. Do I have to pack all of my own stuff?
- Is it illegal to carry anything somebody else packed?
- Or is it OK to say "no" about items I didn't pack and then those items get handled by a separate procedure?
I'm asking this generically rather than about a single country on purpose. If you can provide evidence that at least two countries behave differently then give that as an answer and I will ask a new question about one specific country.
As an epilogue, I was partly wondering in the case of if you were travelling as an air courier, but then I realized I didn't even know if that existed anymore so I asked two independent questions.