I just got through building my own house, and it has two walk in closets. In the average home, they do not put locks on closet doors at all. You would have to personally request a closet door to have a lock on it. I have also looked at many model homes and personal homes over the years in preparing for the building of my home, and those houses did not have walk in closets with locks on them. So the answer is yes, you can open a walk in closet door from the inside. If a lock was added onto this type of closet door and it was locked from the outside, I would think you could not open it from the inside unless you had a key. Most wlak in closets are not made with locks so they can be opened. However some people will specifially ask for locks but there will be a way to open it from the inside.