Celebrities from Danny DeVito to Dave Matthews and Bill Maher lent their voices to a new PSA in favor of California's Proposition 37. The legislation, if passed, would require mandatory labeling of foods containing genetically modified organisms -- commonly known as GMOs.

Sponsored by consumer advocacy group Food & Water Watch, the "Right To Know" video asks California voters to vote "yes" on Prop 37 on November 6.

"Knowing if you're eating or buying genetically engineered food is not your right," DeVito jokes in the video.

Other celebs including Bill Maher, Jillian Michaels, Emily Deschanel, John Cho, Glenn Howerton, Kaitlin Olson, KaDee Strickland and Kristin Bauer van Straten chime in, offering an alternative, such as moving to another country where citizens do have the right to know if their food contains GMOs.

Appearing on the state's November ballot, Prop 37 has been hotly contested with opponents of GMO labels pouring tens of millions of dollars into efforts to defeat the proposition.

For agricultural giants like Monsanto -- one of the so-called "Big Six" -- passage of the ballot measure could greatly hinder its use of genetically-engineered crops.

While the health effects of GMOs remain controversial, the PSA emphasizes that consumers should have the right to know what's in their food, just as nutrition labels list fat, sodium and sugar amounts.

"If there's nothing wrong with GMOs, why not put it on the label," Matthews says in the video, emphasizing, "Made with GMOs!"

Watch the PSA in favor of California's Proposition 37 above, and check out what activists have done to protest GMOs in the gallery below.

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  • A picture taken on October 9, 2008 shows an ultralight helicopter hovering above a field where Greenpeace activists and Austrian organic farming association BIO AUSTRIA wrote the message 'NO GMO' (Genetically Modified Organism) by planting light green coloured organic buckwheat in a field of organic peas in Breitenfurt, some 60 kms south east from Vienna. (DIETER NAGL/AFP/Getty Images)

  • Thirty-five tons of corn put by Greenpace activists at Mexico City's Zocalo Square as a protest against the sowing of transgenic corn, form a map of Mexico on February 26, 2009. (Ronaldo Schemidt/AFP/Getty Images)

  • People walk on a plateform past an advert against genetically modified (GMO) food on February 15, 2011 at a subway station in Paris. (MIGUEL MEDINA/AFP/Getty Images)

  • Greenpeace activists demonstrate against genetically modified organisms (GMOs) on November 24, 2008 in front of EU headquarters in Brussels. Greenpeace called on the European Union to suspend the authorization of GMOs until the EU is capable of evaluating the risks they pose. (DOMINIQUE FAGET/AFP/Getty Images)

  • Greenpeace activists stand a protest in front of Los Pinos presidential residence in Mexico City against the farming of transgenic corn in Mexico, on June 26, 2009. (ALFREDO ESTRELLA/AFP/Getty Images)

  • A Greenpeace activist impersonating Brazil's Chief of Staff Dilma Russeff takes part in a protest against the authorization to grow transgenic rice during a meeting of the National Biosecurity Technical Commission (CYNBIO) at the Science and Technology Ministry in Brasilia October 15, 2009. (JOEDSON ALVES/AFP/Getty Images)

  • Greenpeace activists distribute samples of transgenic rice as part of a protest against the authorization to grow transgenic rice during a meeting of the National Biosecurity Technical Commission (CYNBIO) at the Science and Technology Ministry in Brasilia October 15, 2009. (JOEDSON ALVES/AFP/Getty Images)

  • The logo of French 'Les faucheurs volontaires' (Volunteer trimmers of GMO) is seen as demonstrators stand in front of the booth of French union 'la confederation paysanne' (farmers union) during an action against GMO at the International Agricultural Fair on March 6, 2010 in Paris. The European Commission authorised, on March 2, the cultivation of a genetically modified potato, developed by BASF, the first such green light for 12 years. The issue of so-called 'frankenfoods' has long been a matter of fierce debate in Europe and the commission stressed that the Amflora potato in question would be able to be grown only for 'industrial use' including animal feed, rather than for human consumption. (BERTRAND LANGLOIS/AFP/Getty Images)

  • A couple waves after a parody of union between German chemical giant BASF (L) and the European Food Safety Authority (R) - Autorite europeenne de securite des aliments- (EFSA) during the International Agricultural Fair on March 6, 2010 in Paris. (BERTRAND LANGLOIS/AFP/Getty Images)

  • A giant banner depicting a farm, is seen as Greenpeace activists hold banners to protest against the genetically modified (GMO) food production in front of the parliament building of Budapest on February 10, 2010. (ATTILA KISBENEDEK/AFP/Getty Images)

  • A grey-cow is pictured near Greenpeace activists in traditional Hungarian costume standing in front of a giant banner depicting a farm as others hold a banner reading 'GMO-free Europe' to protest against the genetically modified (GMO) food production in front of the parliament building of Budapest on February 10, 2011 during a demonstration. (ATTILA KISBENEDEK/AFP/Getty Images)

  • Greenpeace activists hold a banner to protest against the genetically modified (GMO) food production in front of the parliament building of Budapest on February 10, 2010. (ATTILA KISBENEDEK/AFP/Getty Images)

  • A man dressed up as a bee holds a placard during a demonstration organized by French Professional Beekeepers Federation (FFAP) to protest against the use of pesticide on September 14, 2011 along the Saint-Bernard quay in Paris. (JACQUES DEMARTHON/AFP/Getty Images)

  • Anti-Genetically Modified Organisms (GMO) demonstrators protest in front of Colmar courthouse on September 28, 2011, eastern France, during the trial of 60 militants accused of destroying MGO plants. (FREDERICK FLORIN/AFP/Getty Images)

  • An anti-GMO activist holds a banner reading 'Science without conscience is but the ruin of soul' during an action to call for the ban of the 'MON 810', a variety of genetically modified maize (corn) developed by Monsanto Company on January 23, 2012 at a Monsanto storehouse in Trebes near Carcassonne, southern France. (ERIC CABANIS/AFP/Getty Images)

  • Is Branding Food With "GMO" the Kiss of Death?

    Prop 37 in California proposes that genetically modified food be labeled "GMO". If you knew your food was genetically modified, would you still eat it?