With the U.S. lifting sanctions against Iran Saturday, Washington will now allow foreign subsidiaries of American companies to trade with Iran, the Treasury Department said, according to Reuters. Authorities have also lifted restrictions on non-American purchases of Iranian oil and sales involving Iran’ s energy sector, the news agency reported.

With the sanctions going away, Iran will likely be ready to conduct new business, but U.S. companies could still encounter obstacles.

“There is not going to be a comprehensive law allowing all U.S. companies to operate in Iran anytime soon. This will make American firms the biggest loser of the nuclear deal,” Majid Rafizadeh, a Middle East scholar at Harvard, told CNNMoney in a story published Monday. In fact, the Treasury Department wrote on its website that “the U.S. embargo will generally remain in place, even after Implementation Day, because of concerns outside of Iran’s nuclear program.”

CNNMoney reported that while the U.S. was set to lift its nuclear sanctions on Iran, many business sanctions would remain and that it would still be very difficult for American businesses to set up a physical presence in Iran or partner with Iranian companies. “In contrast, Europe is opening up almost all trade with Iran,” the site said. “The result is likely to be: European companies win, American companies lose.”

The U.S. was set to lift only a portion of its sanctions on Iran, with the White House saying in July that “U.S. statutory sanctions focused on Iran’s support for terrorism, human-rights abuses and missile activities will remain in effect and continue to be enforced.” 

There remains uncertainty about what exactly will be allowed for American companies, with the Treasury Department saying broadly that the country will allow “the sale of U.S. origin aircraft, parts and services exclusively for commercial passenger aviation to Iran; the import of Iranian-origin carpets and foodstuff; and certain activities conducted by foreign subsidiaries of U.S. companies,” according to NPR.

CNNMoney reported that U.S. businesses would likely have to apply for special licenses to deal directly in Iran, while Europe would be far more open. “As many countries rush to sign contracts with Iran [after Implementation Day], the Obama administration will have to decide to either put U.S. firms at a disadvantage or issue them licenses,” Rafizadeh told the site.