You forgot about importing the key.
wget -O - http://download.videolan.org/pub/debian/videolan-apt.asc | sudo apt-key add -
- [Trisquel-users] Proposal: Update "Enable DVD Playback&q... joelh
- Re: [Trisquel-users] Proposal: Update "Enable DVD P... jason
- Re: [Trisquel-users] Proposal: Update "Enable DVD P... enduzzer
- Re: [Trisquel-users] Proposal: Update "Enable DVD P... xliang9550
- Re: [Trisquel-users] Proposal: Update "Enable DVD P... joelh
- Re: [Trisquel-users] Proposal: Update "Enable D... enduzzer
- [Trisquel-users] Antwort: Proposal: Update "Enable ... t . schieber
- Re: [Trisquel-users] Antwort: Proposal: Update "... Mason Hock
- Re: [Trisquel-users] Proposal: Update "Enab... t . schieber
