Nested forms and deleting/removing has_many associations

I am using nested forms on person model that has many pictures.
I would like to allow the user to remove on or more of the associated
pictures from the person using nested forms as suggested by Ryan B…
However delete will delete the picture not remove the associatioon
I can do it in the controller, but it should be done in the same way as
delete is performed using attribute _delete
Anyone knowing if a _remove attribute is implemented or know any other
way to solve the problem (e.g. that could be a command

Another problem is that it seems as nested forms do not validate the
attributes of the associated object in this case picture.
I have solved the problem by a fix in the controller, but it should
really be a part the nested form

Anyone that has a solution to that problem?

Any comment would be much appreciated