Why the empty briefcase?

In the sci-fi film, Lockout, can someone please explain the empty briefcase, the lighter with the chip inside of it? Why was Snow still arrested even though he was told he would be let go after bringing the President's daughter back to earth safely (basically the ending of the film)?

I enjoyed the film alright. Guy Pearce was awesome, but that ending threw me for a complete and utter loop, it did. I get that they're using the briefcase as a way to lure out the mole, but it still doesn't seem to add up.

plot-explanation lockout

Best Answer

Here is a brief part of the synopsis given on IMDB which states pretty clearly about the parts you are asking:

The suits allow Snow and Emilie to re-enter Earth's atmosphere and parachute to safety in New York City. Emilie is taken to the hospital, while Snow is arrested. At her bed, Emily realizes Mace had actually given them the code "ICUI4CU", which opens the briefcase, hidden in a locker in a subway station with the word "Lullaby" spray painted on it. Emilie then finds evidence the footage of Snow killing Armstrong was forged and delivers the briefcase to Shaw during a meeting with Snow. Shaw opens it, but finds nothing, only to notice that Emilie hadn't told him the code. Realizing Shaw is the mole, Langral arrests him and releases Snow.

Snow retrieves the lighter that Armstrong had given him before dying, only to realize that the microchip with the true evidence and the secrets that Shaw had stolen is hidden inside. Snow decides to keep it for himself in case he needs to use it as leverage.

Unless I'm way off base, the briefcase is a decoy while the lighter is (or has) the true "evidence" ... been a while since I've seen the movie, though.