Yesterday, the House of Representatives passed a bill requiring large food companies to label products containing genetically modified organisms—plants and animals that have had a gene from another organism inserted into their genetic code. The bill is now headed to President Obama, who is expected to sign.

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But the new law is not as straightforward as it sounds. Unlike the European Union, where strict regulations require food products to note whether any ingredient or part of the process producing it involved genetically modified organisms, the new U.S. law has some wiggle room, and not all of the details have been hashed out yet.

Still, the bill represents a compromise that many environmental groups and agribusinesses never thought would happen. Yet both GMO supporters and anti-GMO activists are lukewarm about the final product. “I don't think that it’s the best bill that we could have, but it’s the best bill we could pass,” Richard Wilkins, president of the American Soybean Association, which opposes GMO labeling, tells Dan Charles at NPR.

The pro-labeling groups are also not entirely satisfied. Scott Faber, executive director of the Organic Voices Action Fund, which runs the The Just Label It campaign, tells Charles that his group officially opposes the bill because they believe it's too weak. But he’s still impressed that it made it through Congress. “It’s not an insignificant achievement that a Republican Congress has decided to mandate a national GMO disclosure on every food package that contains genetically engineered ingredients,” he says.

So what exactly is and isn’t in the bill? Here’s a breakdown.

QR Codes, Not Labels

According to the bill, the new labels can include a “text, symbol, or electronic or digital link” which discloses the use of GMOs. It’s a loophole that would allow food manufacturers to put an obscure symbol and Quick Response Code (QR) on their packaging instead of spelling out the fact that it is a GMO product.

Critics argue that consumers will ignore the codes and that populations without smart phones or internet connections will not have access to the information. Jesse Jackson even sent a letter asking President Obama to veto the bill, arguing that it’s discriminatory. Critics also argue that the once-ubiquitous QR codes have already fallen out of fashion. “We don’t think the Q.R. code is a viable or even an honest disclosure,” Gary Hirshberg co-founder of Stonyfield Farms tells Stephanie Strom at The New York Times. “It’s just another way of keeping citizens in the dark—every 13-year-old knows Q.R. codes are dead.”

But Sarah Zhang at Wired sees it differently. She argues that the QR code would link to a website that could lead to a deeper, more nuanced discussion of GMOs.

The FDA and Department of Agriculture Still Have to Weigh In

In many regards, the bill punts when it comes to the details. The labels are not required for another two years and in the meantime, the FDA and Ag department have hash out some of the regulations.

The biggest issue the FDA faces is figuring out how much GM product needs to be present before the food requires labeling. For instance, highly refined oils and products like high-fructose corn syrup have all the genetic materials stripped from them, which some people argue makes them non-GMO. Strom points out that the provision will likely end up in court with judges weighing in on those definitions.

The bill also instructs the FDA to exclude animals that feed on GMO crops, such as cows fed GMO corn, from being labeled as GMO products.

It's All Vermont's Fault

After seven years of knocking down every GMO labeling bill introduced, it only took Congress roughly three weeks to get this new legislation passed. That’s because the State of Vermont forced them to act. In 2014, the state legislature passed a law requiring clear labeling of GMO products, reports Dan Charles and Allison Aubrey at NPR. That law, which went into effect July 1, would force large manufacturers to add GMO labels to products going to all states since it would be too costly for them to label a separate batch of products for the Green Mountain State (or so they argue). Some companies like Campbell’s and Mars added the info to labels; others waited for the Feds to take action.

Their patience was rewarded. The bill includes a provision that nullifies any state laws on GMO labeling, even if it is more strict, giving labeling authority to the FDA.

It Only Includes One Type of GMO

The bill specifically calls out one type of genetic modification, “in vitro recombinant deoxyribonucleic acid (DNA) techniques,” the method by which most currently available GM foods were created. But Zhang at Wired writes that it’s unclear if the bill would cover the newest advances in crop science, in particular CRISPR, a gene editing technique in which certain genes are cut out and added to the DNA. Already the USDA has shown signs that its not too concerned with CRISPR-edited organisms; in April it ruled that a CRISPR mushroom didn’t need to pass its regulatory process.

Is It Worth the Trouble?

While advocates on both sides have battled fiercely and for years over labeling, it’s not clear what impact GMOs have on human health or the environment. A recent review of the first 20 years of GMO crops suggests they are very likely safe to eat and much of the scientific community is leaning heavily toward the pro side of the debate. In late June, a group of 107 Nobel laureates released a letter urging environmental groups to re-examine their stance on GMOs and stop the carte blanche campaigning against “the tools of modern biology.”