executing delete in a case statement?

What is the proper way to execute a delete statement (if possible) in a
case statement. I am trying various versions of the following but can't
get it to work:

"select member_id, case when (select count(buy_later) from cart_li where
member_id=cart_id AND buy_later=true) > 0 then (delete from cart_li
where cart_id=10) end from carts"

Thanks!

Jc