Wealthy Muslims, like everyone else with that kind of money, need private bankers and wealth managers to help them with educating their children, preparing for retirement, funding their chosen lifestyle and ensuring a smooth transition of assets upon their deaths.

But for many advisors in the U.S., it’s a peculiar market—many Muslims require Sharia-compliant investments, but not a lot of financial experts have expertise in Sharia law.

Serving this population as a financial advisor is a tall order, as devout Muslims are prohibited from investing in instruments that generate interest and taking on trading risk without having a real asset underlying the deal. There are also prohibitions on investing in activities prohibited in Islam, such as the consumption of alcohol, tobacco and pork; gambling; pornography; and weapons manufacturing. Hotels, cinemas and music companies are also prohibited, as are conventional insurance and financial services firms.

Moreover, there are also stipulations for a company’s capital structure. For example, accounts receivable must be less than 30% of assets—to ensure the company does not engage in too much lending—and the total debt must be less than 30% of its market capitalization to make sure the firm is not overleveraged.

Satisfying these prohibitions is difficult, as many modern finance instruments, from treasury bills to currency futures, involve lending money on interest, the sale of risk or both. Even real estate investment trusts have become problematic, because if a REIT buys a shopping mall that includes a liquor store or smoke shop, some scholars would say the REIT is no longer Sharia-compliant.

“There’s demand for innovation, but it’s not just creating Sharia-compliant debt. It’s about creating instruments that truly reflect the principles of Islamic finance, which are about profit sharing and risk sharing,” says Shakeeb Saqlain, founder of Islamicbanker.com. He notes that venture capital is a good fit. “The demand is there, but the industry needs something more than just Sharia-compliant loan deals that are simply conventional products re-engineered.”

Saqlain expects innovation in the Islamic finance sector to come as the demand increases.

It won’t be easy, though, says Meagan Froemming, a visiting fellow at Harvard University’s Islamic Legal Studies program. Deals often involve multiple layers to enable them to be Sharia-compliant, and that can lead to added costs, such as double taxation. Getting around the mortgage prohibition might involve a bank buying a house and then selling it back to the owner, but every time the house changes hands, the transaction is taxed, she notes.

“You do multiple transactions and restructure the way returns are granted in order to avoid interest or avoid making money on money, but it becomes a complicated process that may have higher transaction costs,” she says.

Another problem: When the contracts comply with Sharia law, what happens if something goes wrong and they have to be adjudicated? There have been a couple of cases in New Jersey, for instance, where the parties chose to have their case tried under Sharia law and the court agreed to do it.

“American law enables parties to choose which laws they want to apply, but it’s been an issue when people choose Sharia law. What does that mean? And will American courts or U.K. courts see that as a legitimate choice? There’s been no clarity on this issue,” Froemming says.

But one of the biggest issues is the diverging opinions about what makes investments Sharia compliant. While equity-related instruments and businesses that are ethically and socially responsible are generally considered universally acceptable, views on other instruments can differ by scholar, region and sect of Islam.

“The lack of standardization in the industry is a problem,” Froemming says. “There are serious differences of opinion as to what determines what is Sharia compliant in the industry.”

There’s also been skepticism about the endorsement process.