On my quest to see all the Rembrandts in the world I've been to the Mauritshuis, (pro tip; it's pronounced "Mawr-its-house) the Rijksmuseum, and the Louvre and in each case, when I've found myself in front of a painting I can learn a lot from, I pull out my sketchbook and begin a block-in of the major shadow-shapes.
This requires I stand in one place, in front of an oftentimes very popular painting, for at least 20 minutes and often 30. In some museums, I've had people talk to me, telling me my drawing is beautiful.
It's a very nice feeling to work so hard and have someone in passing say they like it. It's also encouraging because it affirms that I'm not in anyone's way nor am I encroaching on their enjoyment of the piece.
When I sketched The Girl With the Pearl Earring, I stood about as close as I could get to her and ignored the milling, mumbling, instagramming throng around me until I finished.
No one disturbed me or huffed and puffed in an irritated way to get me to move from my very prime real estate right in front of her. Easily 50-60 people must have come in, viewed her with the same hushed reverence and moved on. Some selfied in front of her but off to the side so as to not jostle me. I heard Dutch, German and French spoken all around me and still I sketched, mostly oblivious to the hubbub.
I finished my little drawing, rather pleased. I'd learned a great deal about the painting and left happy. I never considered whether or not I had a right to do that until I was talking with an artist friend of mine the other day about drawing in museums.
He asked me if I go when the museums are least busy and I replied that it never occurred to me to do so. He seemed surprised and wondered whether people got annoyed when someone (me) is blocking their view.
It suddenly dawned on me that my philosophy about drawing in museums is that the artist has more right to be there than anyone else. Without artists copying other artists throughout history there would be no art in museums, and maybe there wouldn't be any art.
Think of the cave painters. They copied each other for tens of thousands of years.
The Romans copied the Greeks. The Renaissance artists copied the Romans and the Greeks. And then every generation of artist until the early 20th century copied the greats of the previous centuries, mostly standing in museums.
I have a pet theory that without artists civilization comes to an end. Therefore, in order for civilization to continue, artists need to have access to the work of other artists, and that includes standing in front of paintings for as long as they need to in museums.