brussels european union executive offer initial back thursday franco-german proposal allow permanent border check within bloc free-travel zone five countries so-called schengen travel zone germany france denmark austria norway restart border control 2015 attack paris attempt control movement refugees migrants arrive bloc unprecedented number year schengen rule allow reintroduction frontier control two years ones place expire november germany france aim extension ability reinstate future ask eu change system extend maximum duration four years joint proposal paris berlin see reuters say would require context long-term terrorist threat raft deadly islamist attack europe commission recognize new security challenge appear past years demonstrate recent terrorist attack barcelona turku eu migration chief dimitris avramopoulos tell journalists talk eu interior minister say brussels-based commission would propose update schengen border code late month french interior minister gerard collomb tell journalists talk brussels raise problem time ago german colleague ... hear commissioner indeed want make schengen code flexible ... allow us protect border terrorism eu executive warm franco-german call emergency border check