betcha the brake shoes are holding it on.
There is no retaining ring holding the axles. That spring effect your seeing is probably the brake shoes stuck inside the drums.
your going to have to de-adjust the brakes and hope they haven't worn out so bad that the drum has a ridge in it. If that's the case your going to have to use pry bars and force the drum off which is going to break the brake hardware.
These were always difficult to get off.