Literally every check-in form I've been through had some required checkboxes to declare that you've packed your luggage yourself, have complete awareness of what's in there, and claim responsibility for such items. There are also countless, very visible, posters in airports saying so. Your paper trail might be useful to law enforcement in prosecuting the people who handed you the no-no stuff, but it doesn't absolve you of any responsibility.
Anecdotally, I once had an outrageously difficult time explaining to a German customs officer that the bag I placed in the scanner had items belonging to both my sister and myself. It didn't help that we were travelling together, and she was also there to back my statements up. He simply would not accept the fact that there was an electronic device (e-book) that belonged to her, in a bag that belonged to me, which we forgot to take out before the scanner.
That's not how the world works. You are responsible for the luggage you are transporting even if it's not yours. The customs do not care and they are not going to try to figure out the laws of the place you came from or get in contact with their authority.
> The customs do not care and they are not going to try to figure out the laws of the place you came from or get in contact with their authority
Yes. They also won't try to 'interpret' their own country's laws, it's above their paygrade. If you aren't doing exactly what they expect, they will hold you (or your passport) and push the issue upstairs.
Source: I had this happen to me when I tried to enter Canada to work on a contract for which I should have had a work permit. My company had given me the paperwork appropriate for a salesperson or conference attendee. The officer at the gate confiscated my passport, told me to come back the next day with the correct paperwork, and threatened me with arrest if I failed to return. Stress and long nights ensued.
Yeah, and if the perpetrators have disappeared, the authorities aren't going to say "Oh well, they disappeared, let's hunt them.", but they'll drag the mule into court instead...
Depends on the country, I wouldn’t try it myself. And I’m pretty sure „well I wasn’t even allowed to inspect my luggage, i have it on paper“ isn’t a good defense, because then you shouldn’t have taken it in the first place. If you bring something onto a plane, it’s your responsibility. If you don’t know what it is, don’t take it.
No problem - you have a paper trail showing where you got it, that you were unaware of what was in it, and that you were not allowed to inspect it.