Although stars and non-stars might not be able to object to being photographed in public places (like outside the Vista Theater), the issue here concerns any person's right of publicity and privacy when his or her image is used for profit. Here's a link to a primer on some law in this area:
http://www.publicdomainsherpa.com/rights-of-publicity-and-privacy.html.
When others are selling your image without your knowledge or permission, you have no control over where your image may end up, nor are you compensated for such use. As a practical matter, however, some stars could decide that asserting and enforcing their publicity and privacy rights isn't worth the ire of their fans, so they simply (though not happily) look the other way. The publicity generated by the illegal sales may even be viewed as free publicity for stars who crave it but are no longer in the limelight.
Also, aren't the stars who participate in the fests compensated for their appearances by getting a percentage of the gate? If so, from a purely cold business standpoint, every sale of a video of a fest arguably means one lost ticket sale to that fest -- and, consequently, less compensation for the participating star. Thus, some stars will fight for every dime due them. Obviously, some fans could not have attended anyway due to health or financial reasons and would love a video copy, but the law tends not to favor them. As Midnite says, one could ask JF for advance permission, but it is doubtful he would give it. And even if he would consider giving it, the contract the videographer would have to sign would likely be on terms very favorable to the star and strict against the videographer (I'm straining not to say "draconian").
I suspect that if it even got this far, lawyers would be involved on both sides of the negotiations, and the videographer under consideration would no longer be an individual but rather a corporation like MPI.
Ben