Like all legal questions, it depends.
If someone hired me, my contract said they own the images, negs, and all copyrights. If I hired a model, etc. then I owned all the images, negs and copyrights. If someone wanted to buy a print of something I did, the bill of sale clearly stated that they did not have rights to reproduce or alter the image in anyway. I had clear, plain English contracts and model releases that spelled it all out. Never had any issues.
When I did weddings, I figured they hired me to shoot the pictures and not own or control the rights to them. Their wedding, their images, they own all rights to them. IMHO anyway. I shot a few where I did them for a flat fee and handed all the film over to them and walked away.
If anything turned out really nice I'd ask them for permission to use their image in my portfolio.
As a side note, of all the weddings I shot, none of them are still married now. One of the best wedding images I ever did, the couple didn't even last a year.