can't change lock in info

Almost all pictures that i have are locked. There is closed lock symbol in the infoscreen.

I can open the lock but after closing the infoscreen the lock is closed again.

Point is that it also prevents me to delete this picture on my iPad after sync.

No trash symbol when selecting the picture on the iPad.

The only way to delete is doing so via iPhoto/iTunes.

I can't find the reason it behave so.

Since other, earlier pictures can be deleted. There the trash symbol do appear.

I put this question at MacOS level since it starts at the finder.