With the January transfer window, obviously, comes arrivals and departures. The Champions League knockout rounds start in a couple weeks; UEFA requires each team to submit a list of eligible players prior to the group stages, and after the January transfers, requires clubs to submit updated lists reflecting any changes to club rosters as far as players who are eligible to compete in the Champions League.
That list was released today, and to nobody's surprise, the injured Kim Kallstrom was listed as an eligible player for Arsenal. Sadly, this is also the last nail in the coffin of Emmanuel Frimpong's Arsenal legacy, as he's of course been de-listed since his move to Barnsley (complete with auspicious debut!). The rest of Arsenal's loanees and departures are also on the not eligible side of the ledger.
Is this a big story? No, it probably isn't. But when Kim Kallstrom is healthy, he's eligible to play, and when Arsenal get past Bayern, they will be glad for the additional squad depth.