The law, which had been hailed as a model for other states, is one of a number of state initiatives designed to combat rapidly rising drug prices. It gave the state attorney general power to intervene if a generic or off-patent drug's price increased by 50 percent or more in a single year.

If dissatisfied with the company's justification, the attorney general could have filed suit in state court. Manufacturers would have faced a fine of up to $10,000 and potentially have to reverse the price hike. The generics industry was fiercely critical of the law.

"We are evaluating all options with regard to next steps," said Maryland Attorney General Brian Frosh in a statement. His office would not elaborate further.

The state could appeal to have the case heard "en banc," meaning by the full 4th Circuit, with jurisdiction over five states.

Such appeals aren't commonly granted, but this law could be a strong candidate, suggested Aaron Kesselheim, an associate professor at Harvard Medical School who researches drug-price regulation.

The Friday ruling looms large as other state legislatures grapple with ever-climbing drug prices.

Similar price-gouging legislation has been introduced in at least 13 states this year, though none of those measures became law, according to the National Conference of State Legislatures (NCSL). Three other bills failed to gain passage.

The court's finding could have a chilling effect on such efforts, especially as more state legislatures wrap up business for 2018.

"A negative court ruling will put a damper or a pause on state activities," said Richard Cauchi, NCSL's health program director. "Unless this topic is your No. 1 priority of the year, your legislators are juggling multiple bills, multiple strategies. When bill three gets in trouble, they move to bill four."

The appeals court held that Maryland's law overstepped limits on how states can regulate commerce — specifically, a constitutional ban on states controlling business that takes place outside their borders. The majority ruling argues that since most generics manufacturers and drug wholesalers engage in trade outside Maryland, the state cannot control what prices they charge.

In a dissenting opinion, the panel's third judge argued Maryland can regulate the drug prices charged within the state since the law is meant to affect only medications being sold to its own residents.

Kesselheim, in an article published last month in the journal JAMA, argued a similar point.

Regardless, striking down a law on constitutional grounds can be particularly discouraging, suggested Rachel Sachs, an associate law professor at Washington University in St. Louis who researches drug regulations.

"If it had been a rejection on vagueness grounds, that's something you can cure with a more specific statute," she said. "But the fact that they said this is unconstitutional poses real concern for other states."

That's important. While the federal government has talked a big game on bringing down drug prices, it has done little. Instead, states have taken the lead — spurred by the budget squeeze pricey prescriptions impose on their Medicaid programs and on state employee benefits packages.

But states have far fewer tools at their disposal than does Congress. Most state laws so far tackle only pieces of the problem — targeting a specific drug or particular practice, experts said.

"We'll get more broad and better evolution on this issue if the federal government decides to take it seriously — which it hasn't so far," Kesselheim said.

To be fair, Maryland's law is only one of a bevy of approaches.

Other states have focused on price transparency laws. In California, drug companies must disclose in advance if a price might increase by more than a set percent and that they justify the increase. Industry has sued to block the California law.

New York has limited what the state will pay for drugs, establishing a process to review if expensive drugs are priced out of step with their medical value.

A number of states have since 2017 passed laws regulating pharmacy benefit managers — the contractors who negotiate discounted drug coverage for insurance plans, but who rarely reveal what level of discount they actually pass on to consumers.

Experts expect that activity to continue, especially as escalating drug prices show little sign of letting up.

"The states are going to keep trying and experimenting," Sachs added. "This is a problem that isn't going away."

Even efforts such as Maryland's — which targeted price-gouging — will likely remain at the forefront.

"I don't think this is the end of states trying to do something on price-gouging," said Ellen Albritton, a senior policy analyst at the left-leaning advocacy group Families USA who consults with states on drug-pricing policy. "It's such an issue that offends people's sensibilities. It's crazy people can do this."

Kaiser Health News is a nonprofit news service covering health issues. It is an editorially independent program of the Kaiser Family Foundation, which is not affiliated with Kaiser Permanente.