Intellectual property is one of the most vexing issues of the digital era. Across the planet, more and more people are exchanging music, software, images, televison programmes, and even whole movies over the internet. It's not surprising then that traditional media companies are terrified: the old business model has been predicated on Big Media being able to control the distribution channels - be it CDs, DVDs, television, and so on - but digital technology and the internet have changed everything. Users are becoming more sophisticated at ripping, editing, and sharing digitised content for free across the wires using peer-to-peer software. It may not always be strictly copyright legal, but as media conglomerates are discovering at great expense there's little they can do to prevent this growing trend.

RiP: A Remix Manifesto, a feisty, NFB-produced documentary showing at the Whistler Film Festival (4 - 7th December), is a call to overhaul copyright laws. As the title suggests, RiP is particularly interested in the legally grey area of remixing existing works, although director Brett Gaylor also introduces individual mom 'n' pop downloaders who have been stamped on by the heavy boot of the litigious music industry: high school kids, a Texan pastor, and Jammie Thomas, the single mom who was ordered to pay the recording industry $222,000 for allegedly downloading 24 songs. By criminalising its customers the music industry has set itself up for attack and Gaylor has great fun mocking its bully boy tactics.

RiP focuses in particular trendy, laptop musician Girl Talk (aka Gregg Gillis) a Pittsburgh biomedical engineer who mashes-up hundreds of samples from other artists' works into his own distinctive compositions. The film suggests that artists have borrowed from their predecessors since time immemorial and that digital mash-ups are just an extension of that. What's more the cost of getting clearance for Girl Talk to perform the songs would be prohibitive. So he doesn't, although the threat of litigation always hovers over his head. Gaylor memorably makes the point about how copyright is stifling creativity by teasing us with footage of a Girl Talk gig where everyone is clearly having a great time (including Paris Hilton), but the soundtrack is muted. He uses the same device with the song "Happy Birthday" - owned by Time Warner - to show how absurd copyright law can be when taken to its natural conclusion.

This is the kind of film where everyone is either a villain or hero. Metallica and the Rolling Stones come off badly as big-business recording artists, while Radiohead, who released their album direct to the web for whatever price fans wanted to pay for it, appear progressive. Star interviewee is Lawrence Lessig, the Stanford Prof who came up with the ubiquitous Creative Commons licence and helped make redefining copyright laws one of the blogosphere's cause célèbres.

Manifestos aren't subtle things: big media is not quite as loony as it appears here. Some artists wont warm to the message that "times are changing: get used to it." But RiP's campaign-style approach still pays off with an entertaining 80 minutes complete with snappy, video mash-ups and montages.

You can contribute to a remix of the film at www.opensourcecinema.org.