Originally Posted by natcin

completely agree with you on all points, but just have to point something out from experience.

earlier this year, i was taking an international flight leaving CDG (not transit, but i would assume its the same), right after i passed both border passport control AND security check, i realized that i had lost 1 of my 2 phones. i clearly remembered that it was with me at the airport prior to check-in. at this point, i approached a random staff who happened to walk by me, and asked how i could get back on the land-side of the airport to hopefully find my phone (i was guessing it had slipped out of my pocket while i was sitting and waiting for check-in to start).

she pointed me to a pathway right next to the security where i just entered from, and that lead me right out to the shuttle tram thingy which i took after leaving border control and before security check (can't remember which terminal). taking the opposite direction on the shuttle leads to arrival immigration where i presented my passport and re-entered paris easily, telling the border customs officer that i was going back out to look for a lost personal item, and was let through.

so from my experience, exiting airside isn't that difficult, of course all this is moot if the different terminals have different paths set up. but in my case, there is no obvious route to do a u-turn out, but a almost obscure pathway right next to the regular security checkpoint before entering airside that leads (via shuttle) right to arrival immigration which i only noticed after the staff pointed it out to me.