This post has been updated.

Donald Trump's son-in-law, Jared Kushner, will serve as a senior adviser to the Trump White House, The Post's John Wagner and Ashley Parker have confirmed.

The news isn't surprising, given Kushner's closeness to Trump and the fact that his potential role in the administration has been rumored for weeks. But it does open up a can of worms — both legally and ethically.

The big question looming over the selection is the question of whether Kushner, who is married to Ivanka Trump, actually can work in the White House. To make it happen, he'll have to get around an anti-nepotism law that dates to Robert F. Kennedy. As I explained a while back:

After President John F. Kennedy appointed his 35-year-old brother, Robert, as attorney general — a basically unprecedented move at the time, involving an office for which few thought the younger Kennedy was qualified — Congress in 1967 passed an anti-nepotism law. . . .
But it's not completely clear whether this law applies specifically to White House staff. In other words, Kushner certainly couldn't be a Cabinet secretary, but the Trump team seems to think he could be an adviser. And the possible precedent for that traces back to another famous political family: the Clintons.
When President Bill Clinton appointed his wife, Hillary, to head up his health-care efforts, the couple was sued. It wasn't that the filers wanted to nail the Clintons for nepotism, but given that she could not be an official government employee under the law, they argued that the meeting of her health-care task force should be open to the public.
The appeals court decision that resulted might have given Kushner and Trump hope to get around the law in 2016, though some experts are dubious.

The passage in question is from D.C. Circuit Court Judge Laurence Silberman in a 1993 decision involving Hillary Clinton's work in the White House, and it says the court doubted “that Congress intended to include the White House or the Executive Office of the President” in the law.

But it's untested in practical terms. And Kushner has long been huddling with lawyers to try to figure out a way around it, including possibly accepting no paycheck and putting his assets in a blind trust, as the New York Times reported in mid-November. (Kushner is a wealthy real estate developer, like Trump, and he owns the New York Observer.)

The process had already begun before Monday. Lawyer Jamie Gorelick, who has been working with Kushner, said in a statement this weekend that Kushner has consulted with the Office of Government Ethics and was resigning from his real estate company.

“Although plans are not finalized, Mr. Kushner would resign from his position at Kushner Companies and divest substantial assets in accordance with federal guidelines,” Gorelick said, adding that Kushner “would recuse from particular matters that would have a direct and predictable effect on his remaining financial interests. He would also abide by federal rules requiring impartiality in particular matters involving specific parties.”

Kushner and the incoming Trump administration had previously foreclosed one potentially major conflict of interest involving Kushner, with Trump announcing last month that his oldest sons, Donald Jr. and Eric, would run his business but Ivanka Trump wouldn't. Previously, the plan was for all three of them to run the business. Ivanka Trump's exclusion was seen as an indicator that she, like Kushner, might try to take an official role. And the two of them recently bought a house in Washington.

Update: A lawyer assisting the Trump family says Ivanka Trump will not immediately take on a formal role in the White House.

But should Trump attempt to install both Kushner and Ivanka Trump into his administration — or even simply involve Ivanka Trump in an unofficial capacity — it will likely only ratchet up the debate about whether it's appropriate to have one's relatives so close to the levers of power. Whether the 1967 federal anti-nepotism law covers Kushner and Ivanka Trump, it's clear that nepotism has been a concern for lawmakers before. Putting two more close members of a president's family into the White House, should Ivanka Trump have an official role, would certainly revive that debate in a way we haven't seen since the Kennedys.

In other words, for an incoming administration that already has an unprecedented number of ethical questions and conflicts of interest hanging over it, you can add one to the pile. And for a guy who pledged to drain the swamp, Trump has sure been willing to stretch the ethical and legal bounds of the office he's about to assume.