Sharks may have a friend in Congress. Bipartisan proposals in both houses of Congress aim for a federal ban on shark fin, a measure aimed at protecting global stocks of sharks. But some shark scientists, including the well-respected David Shiffman, actually oppose the ban, arguing that since the U.S. shark fishery is well-managed it can export expertise, serving as a good example for others to wisely manage their shark stocks. There is heated debate about the issue, but one thing is certain: when it comes to conservation, sharks are tricky. Since sharks are slow-growing and long-lived, once shark stocks are depleted, they take a while to rebound.

The high demand is thanks to shark fin soup, an Asian delicacy once reserved for the very wealthy but now affordable to the growing middle class. Fins are relatively light, small, and easy to preserve, compared to the bulky body of the shark. To maximize revenue—keeping the entire shark body takes up space that could be used for the more valuable fins—the inhumane practice of finning arose, in which a shark is caught, the fins removed, and the creature tossed overboard still alive. Unable to swim, the poor creature will die from starvation or drowning.

Fortunately, the U.S. and most fisheries have banned this cruel practice. In the U.S., all fins landed must be attached to a body. But a U.S. ban on detached fins does not apply to imports or exports, easily allowing fins of uncertain or illegal origin to enter domestic supply. Deciding that U.S. regulations were insufficient to protect shark stocks, California and several other states decided to completely ban shark fins. If all fins were illegal, the thinking went, then there would be no way to inadvertently support poor fisheries practices.

But state bans are not foolproof. Most sharks are harvested in federal waters, not state, so a lawsuit was filed in California arguing that the state law was trying to usurp federal law by applying state rules to a federal jurisdiction. Finally, in the decision Chinatown Neighborhood Association vs. Harris, a federal appeals court denied the suit. State bans remain the law of the land today.

As for a federal ban, the experience with ivory provides some comparison. An international moratorium on ivory was declared in 1989, stabilizing plummeting elephant populations. But the success didn’t last, and widespread poaching soon resumed. Additionally, several countries with confiscated ivory stockpiles argued for the right to sell them, ostensibly in order to earn money for conservation. But it is difficult to ensure that the legal trade does not provide cover for poached ivory, and the sale was eventually denied.

The 1989 ivory moratorium was global. The current shark conservation bills being discussed, however, apply only to the U.S., which is not the center of shark fin demand. Long-term, regardless of how Congress votes, possibly the sharks’ best chance is a change in consumer behavior. Since 2014, demand for shark fin in Asia, the main market, began to decline. The ocean is vast and saving sharks on the high seas is very difficult. The tangled international networks of trade both legal and illegal are even more difficult to police; so let’s hope this trend of declining demand continues.