If I were contracting directly with the couple I'd probably have similar language. I shoot weddings as a contract photographer, so the studio's contract is something over which I have no control. My suspicion is that these GWC situations do impact the studio's sales, but again, its beyond my control.
When I notice that the couple or group has wondering eyes, I just stop, look at the photographer that is distracting them and say, loud enough for the couple to hear, "when you're done, I'd like to get some pictures too". That, invariably, gets the couple to say something.
This situation was a little different, not so much that he was causing me problems, (he was, for the most part, shooting over my shoulder) rather that he had the images on an IPAD sharing them with guests while mine were still on memory cards waiting from me to get them to the studio.
All the talk about we're professionals so our pictures are better is, to me, a little trite. In this situation especially, we were outside, he had essentially the same camera and lens, and he was shooting from essentially the same angles most of the time, in locations that I selected and where I had setup the couple or wedding party. So, all the professional work was done, all that was left was for him to click the shutter. 
Candyann; "pro photographer" or "pro cameras" how are these defined in your contract? I hope it was written by an attorney and that you have thought about the potential impact on your future business if you do stop providing your professional services.
I get the point you are trying to make, I also have a sense that the outcome could be far worse than you may anticipate.
I've shot weddings where the bride's family were all "part time pros" I have a shot of three of them aiming cameras at the bride while she is getting her hair done.
Yesterday I shot a wedding where the bride's sister had a "pro-sumer" camera. One that I've had second photographers working with me use, so it would certainly fit the intent of your contract. It was out and she was taking pictures while they were getting ready, it was out through out the day, often with her husband or a friend shooting. When were were doing the group shots at the Gazebo (outdoor wedding at a country club) she was taking pictures from a few feet at my left. I next shot was the wedding party; I asked her to bring her camera (she was a BM) got them all setup, then told everyone to look at the bride and asked her to point her camera at the bride, then I took my picture.
Point is, there will always be people with cameras distracting the people you are shooting. Mostly because you are shooting. How many times have we all heard "Oh, isn't that a sweet picture" just before about 12 flashes pop around us? 
Back to the contract language; The reason I said I'd include it is not so I can enforce it, but so I can talk to the couple about it during the meetings about their wedding, and then remind them or the parents about it if something is getting out of hand. I would NEVER stop shooting, I might not deliver the proofs until we had a conversation. 