Can the nursing home require me to submit a letter of agreement before I can see my Mother?

I have complained about my Mother's care and have a validated complaint filed with the NYS Department of Health. My brother, after receiving communication by the nursing home (which I was not informed of) has told the nursing home not to let me see my Mother until I have agreed to limit my time with her. The nursing home has required me to write a signed document agreeing to limit my time with my mother. My brother, who has health proxy has agreed with them that I need to provide this letter before they allow me to see my Mother. My Dad, who is very angry about this - has told my brother and the nursing home that this is not his wishes.