My previous suggestion in regards to withdrawing from CAIN stemmed largely from treaty changes that would have fundamentally altered the organisation and the nature of TSP's relationship with it. Considering that this is no longer being considered, I'm largely apathetic towards it.

It essentially comes down to a simple cost/benefit analysis, as Cormac has laid out. So long as remaining in CAIN doesn't cost us anything, whilst producing some benefit for us - in this case, it helps our relationships with several existing allies and creates avenues to develop new relationships with non-allies - it's in our best interest to do so.