If you like going to the park to feed the ducks, you can thank the Migratory Bird Act of 1918.

“Ducks were nearly eliminated at one point," says Steve Holmer, vice president of policy for the American Bird Conservancy. "But through the law and through the effort of conservation, there has been a complete turnaround."

For decades, the act has prohibited people and companies from killing too many birds either intentionally or unintentionally. That means companies need to try to protect birds against accidental deaths that occur as part of their business.

One example, Holmer says, are nets that oil and gas companies put over oil pits to keep birds out. Without the nets, the birds mistake the pits for ponds and fly right into them.

"And because it's oil, or some kind of toxic waste, that is sometimes enough to cause them to die,” Holmer says.

But the nets will no longer be required, he says, because the Department of the Interior’s new interpretation of the law says companies don’t need to worry about accidentally killing birds.

“Under this new interpretation of the law, the companies are completely let off the hook,” Holmer says.

It’s one of a stream of regulatory rollbacks that’s made headlines since President Trump took office. In many cases, though, the announcements don’t mean a permanent end to the regulation, just the beginning of a fight over it.

KUT's Mose Buchele reports

“There’s lots of instances of the Trump administration announcing big rollbacks of environmental regulations. Those get a lot of attention,” says David Spence, a professor of law, politics and regulation at UT Austin. “But the actual process of changing the rules is much more difficult and burdensome.”

To change rules, agencies must follow a process that includes taking public input and creating a rationale for the change. After all that, the government can still be sued over the rule change.

But the Department of Interior did not go that route. Rather than announcing it would “change” the rule, it simply issued a memo stating previous administrations had misread it.

“It’s a lot easier when it’s an interpretation than when you’re trying to change a regulation,” Spence says.

That doesn’t mean there won’t be lawsuits. In fact, there already have been.

The American Bird Conservancy and other groups sued last week, arguing that the change to the Migratory Bird Act needs to go through an administrative process.

“They're basically claiming the memorandum [to reinterpret the rule] was arbitrary and capricious,” says Tracy Hester, who teaches at the University of Houston Law Center.

Hester says if the lawsuit is successful, that could send a message to the administration to be careful how creatively it reinterprets longstanding law.

But there’s no guarantee the conservationists will prevail.

If they don’t, Holmer says, his group may be stuck hoping that whatever administration comes after Trump’s reverts back to the law's previous interpretation.