Are documentary filmmakers journalists?

FORTUNE -- A federal appeals judge in New York will hear arguments today in what's shaping up to be a key First Amendment case. Joe Berlinger, the filmmaker behind the documentary Crude, is fighting Chevron, which successfully demanded all 600 hours of Berlinger's footage in federal court in May.

Berlinger, supported by many media companies and members of the filmmaking community, hopes the appeals court will reverse the ruling and protect the footage under journalist's privilege. For more on this case, see The Media vs. Chevron: Bring It On.

Among those most notable in support of Berlinger is Robert Redford, founder of the Sundance Institute and its corresponding Sundance Film Festival and Sundance Channel. He is an outspoken advocate of independent film and environmental issues, and Fortune asked him for his take on the Berlinger case.

You recently wrote an editorial piece on Huffington Post supporting Joe Berlinger in his legal fight with Chevron. Why do you find this case so important?

For me, if you boil it down to fundamental stuff, it's First Amendment rights and freedom of expression. If Chevron (CVX, Fortune 500) wins this case, it's going to mark the biggest turnover of journalistic work in history. I don't know of another case that would be as consequential.

Do you consider documentary filmmakers to also be journalists?

I think independent filmmakers, documentary filmmakers -- they are journalists. I'm not a lawyer, but I do know this: we need to protect our ability to tell controversial stories. More filmmakers are taking up this mantle. They are doing some of the best investigative journalism right now, as the line between journalism and entertainment is getting blurred.

So you believe filmmakers should be protected under journalist's privilege? And do you think their legal protections are strong enough?

I think documentary filmmakers need as much protection as possible under journalist's privilege. How else is the public to know what is going on? What we're going to see here is not just exclusive to the Chevron case. It could be spread into the BP (BP) case. When the collusion between big corporations and certain members of government has been so strong for decades, they control the message.

So this concern led you to speak out on Berlinger's behalf?

A lot of this stuff becomes personal. I started Sundance to promote and keep alive the value of independent thinking and product. The Sundance Channel was meant to then distribute some of these stories that the public wasn't getting to see. The challenges facing documentary film are huge, and we've got to keep it alive. It's probably going to be an uphill battle, as it usually has been.

Did your work on the films The Candidate and All the President's Men change your perception of journalism?

I'd been on both sides of interviews -- some people had come after me and others complimented me. Once I got into [All the President's Men], I realized how incredibly valuable investigative journalism is. I felt lucky to hook into something at the highest point of journalism. I assumed things would roar from there, and I got shattered to see the downward slide of the next 20 years.

I still think investigative journalism is keeping us intact. I think we're going to be fighting an uphill battle to keep this alive, but if we can protect the rights, the public is going to get more and more attuned to them. The focus of entertainment is taking away from what the public needs as news. I think investigative journalism will always be important and always find its way, be it on the Internet or wherever.