Late last week, the Interior Department issued a legal memorandum ruling that businesses that accidentally kill nongame migratory birds during their operations are not in violation of the Migratory Bird Treaty Act of 1918.

The opinion is a reversal of the policies of previous administrations that sometimes prosecuted industries for accidentally killing or failing to safeguard migratory birds in their operations, reports Jennifer A. Dlouhy at Bloomberg.

Whatever your opinion on the current change, there’s no debating the Migratory Bird Treaty Act has made a huge impact on birds in North America. Here are five things to know about the embattled statute:

Hats Made the Law Necessary

In the 1800s and early 1900s, the United States saw the troubling extinction of several species of birds, including the Heath hen, Great auk, Labrador duck, Carolina parakeet and most troubling of all, the passenger pigeon, once the most numerous bird on the continent.

Most of those were hunted for food, but in the late 1800s, birds faced a new threat: Fashion. As William Souder reported in Smithsonian Magazine in 2013, some 50 North American bird species, including great egrets, snowy egrets and great blue herons were being hunted for their plumes, which were added to fashionable women’s hats. In some cases, entire taxidermy birds were sewn to the headgear.

The market hunting of feathers wiped out entire colonies of the birds, especially in Florida, leading to calls for regulation and the establishment of the National Audubon Society. It was also a major factor in the establishment of the Migratory Bird Act Treaty—initially the American end of a songbird treaty with Great Britain on behalf of Canada, which forbade the killing of many insectivorous native birds, messing with any egg or nest or capturing and transporting birds over state lines.

The Scope of Enforcement Changed in the 1970s

In the 1972, Audubon reports an amendment added 32 families of birds to the treaty, including owls, hawks and eagles, bringing to protection to 1,026 bird species, almost every native bird on the continent or any bird that strays into the U.S.

Around that time, Christopher Brooks for the American Bar Association’s Trends newsletter reports, the Fish and Wildlife Service (FWS) began prosecuting industry practices that needlessly killed birds. In the early days, most enforcement of the Migratory Bird Act was focused on hunters and people directly assaulting birds. The change in prosecution has since led to a split in the courts, with some federal benches ruling that the treaty only applies to hunters and trappers and others saying it’s broad enough to cover industry practices.

To lay out the rules more clearly and create a permitting system for industries that kill or incidentally “take” birds, in 2015 the FWS began the process of creating a modern framework for the law, Brooks reports. That same year, two bills were introduced by the Republican-controlled House of Representatives, which included proposed legislation to slash the scope as well as the financial enforcement of the Migratory Bird Treaty Act, though neither bill made it past the House. In February 2017, the Department of the Interior stopped the FWS rulemaking process. Now, the new memo bypasses Congress and the courts to establish how and against whom the law will be enforced.

Under the new rule, only intentional killing of birds like hunting or trapping can be prosecuted. Dlouhy of Bloomberg reports that supporters of the change say federal prosecutors had too much leeway in previous administrations and that they charged companies unequally, fining fossil fuel producers for killing birds while ignoring bird deaths caused by industries like wind farms.

“During the Obama administration, seven oil and natural gas companies were prosecuted for killing 28 birds at the same time that wind energy companies were allowed to kill thousands of birds, including bald and golden eagles,” president of the Western Energy Alliance Kathleen Sgamma tells Dlouhy. “Today’s solicitor’s opinion returns the rule of law and will help prevent the disparate treatment of industries.”

Conservationists disagree, saying the opinion opens the door for a new level of disregard for the environment. “By acting to end industries’ responsibility to avoid millions of gruesome bird deaths per year, the White House is parting ways with more than 100 years of conservation legacy,” David O’Neill, chief conservation officer at the National Audubon Society, says in a statement. He points out that power lines kill up to 175 million birds per year in the U.S., communications towers kill up to 50 million, oil waste pits trap up to one million and though data on gas flare-related deaths has not been reliably tracked, at least one incident in Canada attracted and roasted 7,500 birds in 2013.

Wind Farms Have Been Fined Too

Wind farms, which the Fish & Wildlife Service estimates kills 500,000 birds per year, have, in fact, also been prosecuted under the act. While proponents of the change in regulation argue that fossil fuel industries have been unfairly targeted by the law, wind farms have received some of the largest penalties in recent years. Dina Cappiello at the Associated Press reports that in 2013, Duke Energy became the first when it was fined $1 million for the deaths of 14 golden eagles and 149 other birds associated with two wind facilities in Wyoming. The AP also reports that in 2014, Pacificorp Energy, also in Wyoming, was fined $2.5 million after it knowingly built wind energy projects in areas with high eagle numbers

The Law Has Screwed Up Your Favorite Movies

Bird nerds are regularly enraged by movies and television shows that play the scream of a native red-tailed hawk then show an African eagle landing a tree or show a dozen non-native songbirds hopping around a bird feeder. That’s because, as Nicholas Lund at The Washington Post reports, it’s illegal to capture and own much less train almost all native bird species. So animal wranglers in Tinsel Town have to get their birds from areas where protections aren’t so strong.

And while that’s a pretty valid reason for Hollywood to get birds wrong on screen, there’s no excuse for the way they screw up bird song. The bald eagle, for instance, has a very weak, almost pathetic call, yet in most shows it’s given the red-tailed hawk’s mighty scream. There ought to be a law about that.

The Treaty Still Makes Children Outlaws

If your favorite niece picks up a pretty blue jay or cardinal feather off the lawn and stuffs it in her pocket, she is technically violating the law. While it’s highly unlikely game wardens will swoop down and arrest her, it’s hard to know how a feather—which most birds molt every year—was obtained, whether it was found or plucked from a hunted bird. So there’s a blanket prohibition on possessing them. Eagle feathers even have their own stricter law. The Bald and Golden Eagle Protection Act, passed in 1940, can result in the a $5,000 fine and year in jail for possessing a single feather. The exception is federally recognized Indian tribes, whose members can possess and use eagle feathers in religious ceremonies. However, even that is controversial, since it excludes members of smaller tribes who do not have federally recognized status.