Any mass expulsions of Afghan migrants would be breach of community law under the asylum procedures directive (The Council directive 2005/85/EC of 1/12/2005 on minimum standards on procedures in members states for granting and withdrawing refugee status) and the qualifications directive (Council directive 24/83/EC of 29/4/2004 on minimum standards for the qualification and status of third country nationals or stateless persons as refugees or as persons who otherwise in need of international protection and the content of the protection granted).

For afghans to be rounded up in northern France and put on a plane without the opportunity of claiming asylum, or if they do have the opportunity to claim without having appropriate scrutiny and procedure, would be in breach of the council directive on the minimum standards for the reception of asylum seekers (Council directive 2003/9/EC of 27/1/2003 which lays down minimum standards for the reception of asylum seekers – covering their detention, access to housing and general support).

MEPs could ask that the French government follow the minimum standards obligations that exist in the procedures directive for the treatment of any asylum claims of any Afghans.

Its about where they are being removed to . If being sent to Greece or any other European country of first entry, under the Dublin Convention, there are still issues about how they're dealt with under council directives, but if they are being sent to Kabul on deportation flights that would raise clear concerns about giving those Afghans the opportunity to claim asylum in France before their removal to Kabul and for that claim to be considered in line with obligations.
Also:
Article 4 Protocol 4 (civil imprisonment, free movement, expulsion) of the European Convention on Human Rights specifically prohibits the collective expulsion of foreigners.
Whilst the UK has signed but never ratified Protocol 4, France has both signed and ratified.

Information about violation of European Convention on Human Rights
 http://www.statewatch.org/news/2002/feb/05belgium.htm

Information about Expulsions of aliens in international human rights law
 http://www2.ohchr.org/english/issues/migration/taskforce/docs/Discussion-paper-expulsions.pdf