demo tape

My band recorded a demo tape of four songs in which I co-wrote three of the songs. The band broke up, but now, my co-writer wants to re-release the songs (as originally recorded) on a cd under his own name. What are the legal implications of this? Can he even do that?
Any insights are greatly appreciated. Thanks!

It is not his property --- but your joint property -- and a letter from a lawyer stating so will get him to stop cold, or at least put him on notice that it is not his and he'd face big liability -- as would anyone buying it.

The real issue is what do you guys want to do as a group even though you broke up?

Moe,
Thanks for replying! I appreciate your advice very much. I've advised my former co-writer that he does not have my permission to re-release that album as it was recorded originally. I'm waiting to see what other tricks he pulls out of his sleeve. As another option (!), he has solicited my help to re-record the songs, but still release the cd under his name. But, at the risk of pouring out this whole drama like a bad soap opera, I will stop here.
Thanks again,
Evian