Unfortunately, there are no more Premium Elite Memberships being sold.

I undertsand you're getting the message saying you need Premium membership to enlist in Clan activities, but it's complicated explaining it all. I hope you're able to translate without losing the point.

Ever since the announcement was made to make Elite a free service, production for Elite Premium were stopped once it was sold out.

One of the advantages of Premium memberships is being able to enlist in Clan activities. Since Elite is now free it would not be fair to those who bought Elite Premium (especially those who bought Premium when DLC4 came out) if free members will have the same advantage they have.

Most likely, the free Elite memberships are geared more for Black Ops 2.

I know there's confusion with all of this and I wish the developers and publishers could have explained it more rather than assume that gamers would understand what they meant with making Elite free but still requiring Elite Premium membership when it comes to Clans.

I hope that I was able to atleast shed some light even if I'm not able to completely answer your question.