there is no such thing as protection for celebrities or public figures, in regards to photography, at the federal level in the US. you can legally film and sell anything that is not expressly prohibited by law (such as child pornography, or filming in a person's private home without their knowledge).
however, in the state of california, there are strict laws that protect celebrities in regards to photography, but they only apply to jurisdiction in the state of california, and they do not apply to the rest of the country.
the liability in regards to infringement is always taken by the buyer of the photo who intends to use it for presentation to the general public.
in the Supreme Court case Sony Corp. of America v. Universal City Studios, Inc., the court ruled that anything that has substantive legal uses is legal (even though betamax could record copyrighted videos). stock photography has substantive legal uses and is therefor legal.
according to Fair Use, all stock photography is legal because all stock photography can be used for commentary purposes. this is expressly written and codified in US copyright law.
1. photographers have the lowest (almost no) risk of copyright infringement
2. stock media agencies have some risk but are protected by the Safe Harbor provisions of the DMCA
3. media buyers have high risk of copyright infringement, if done improperly