Affaires means (court) cases here.

Sarkozy is "sent back" / "returned" to his various cases, i.e. he is kind of expelled from the "old wise man" position he was slightly reaching to a much more unconfortable one where he has to defend himself against various charges.

Here are similar French idioms, often used figuratively :

• renvoyé à ses (chères) études : dismissed, sent back to school

• renvoyé dans ses foyers : demobilized, sent back home

• renvoyé dans ses cordes : sent on the ropes (like in a boxing ring)

• renvoyé dans ses buts : sent back to his goal line/posts (soccer), sent packing

• renvoyé à ses démons : sent back to his personal demons