It&#x27;s possible even with Schengen. A clause in the Schengen convention (in article 2.2) authorizes states to reinstate border checks in exceptional circumstances.<p>&gt; Where there is a serious threat to public policy or internal security, these countries may exceptionally reintroduce border controls at its internal borders for a period of no more than 30 days (possible to prolong under conditions established by the code) or for the foreseeable duration of the serious threat. This action should be seen as a last resort.<p>source: <a href="http:&#x2F;&#x2F;eur-lex.europa.eu&#x2F;legal-content&#x2F;EN&#x2F;TXT&#x2F;?uri=uriserv:l14514" rel="nofollow">http:&#x2F;&#x2F;eur-lex.europa.eu&#x2F;legal-content&#x2F;EN&#x2F;TXT&#x2F;?uri=uriserv:l...</a><p>France was actually going to reinstate some border checks from November 13 to December 13 for the COP21.