"The White House lawyers got it wrong when they tried to make her a nonemployee and pretended that she was exempt from the ethics rules. They were playing games, and that's just not going to work," said Richard Painter, the chief White House ethics lawyer under George W. Bush.
Kathleen Clark, a legal ethics expert and professor at Washington University in St. Louis, said that the White House's former position was "indefensible" and that "that 'voluntary' language really obscured the point — they are claiming that she had a choice."
As a federal employee, Trump is subject to a criminal federal conflicts of interest law that prohibits most federal officials from participating in government matters in which they or their family members have a financial interest. As president, her father, Donald Trump, is exempt from this rule.
Clark and Painter said that Ivanka Trump is not required to divest from her company but that she should recuse herself from matters that could affect her economic positions, her company or her husband's business dealings.
"For example, half of her business is based on jewelry, so pretend the administration is weighing an enormous tax on jewelry," Clark said. "That's something she would not be able to be in the room for if she doesn't fully divest. But it's unclear how broadly this would be applied."
Painter said that Trump should stay away from any trade negotiations with countries where she has manufacturing deals for her clothing brand, as well as from real estate matters.
But Gary Bass, an ethics professor at Georgetown University's McCourt School of Public Policy, said that this strategy is fraught.
The White House "is becoming a family operation, and there aren't a lot of rules about this," Bass added.
In her new position, Trump could run afoul of an anti-nepotism law, some experts believe. But Painter told ABC News that superseding laws, as interpreted by the Justice Department, essentially give the president "unfettered discretion to hire whoever he wants."
Yesterday the White House released a statement about the move, saying that it is "pleased."
"Ivanka's service as an unpaid employee furthers our commitment to ethics, transparency and compliance and affords her increased opportunities to lead initiatives driving real policy benefits for the American public that would not have been available to her previously."
ABC News' Alex Mallin contributed to this report.