There are a fair few US legal experts out there who believe Donald Trump Jr. broke federal law by meeting a Russian lawyer with the hope of getting damning information, which he had been told (paywall) came from the Russian government, on Hillary Clinton, his father’s opponent in the 2016 US presidential race.

Here’s a breakdown of what the law says and how it might apply in this case.

What does the law in question cover, exactly?

The “prohibition on contributions, donations, expenditures, independent expenditures, and disbursements by foreign nationals.”

What does it do?

Broadly speaking, it makes it illegal for foreign citizens who aren’t US residents to contribute to election campaigns.

What does “contributing” mean?

That’s just the question. The law covers a whole range of potential help, but the key point for this case is that the law decrees a foreigner can’t provide any “thing of value” to a campaign. “Thing of value” is a pretty amorphous term to cover a pretty amorphous range of contributions, but election-law expert Rick Hasen at the University of California, Irvine, says it tends to be “read broadly” in the courts—suggesting, as Hasen recently blogged, that damaging information gathered by a foreign government about your opponent can fall under that umbrella.

But as far as we know, Donald Jr. didn’t actually get the information, right?

Unfortunately for him, that’s not actually relevant under the law. It quite clearly says that US citizens can’t “knowingly solicit” contributions from foreign nationals. That leaves two questions: 1. Did he know that the lawyer, Natalia Veselnitskaya, was foreign? 2. Did he “solicit” the information?

The answer to the first question is pretty clear—in the chain of emails to arrange the meeting, which Trump Jr. tweeted out today (July 11), she’s described as a “Russian government lawyer.” As for the second question, Trump tells an intermediary about the information: “if it’s what you say I love it,” and goes on to arrange a meeting to get hold of it. According to Hasen, this is clear-cut solicitation.

So, what happens? Does Trump Jr. go to jail?

Hasen says the case is “no slam dunk” and that it depends on how the courts interpret the “thing of value” clause, and also whether it rules that a violation, if there was one, merits a criminal sentence. Ryan Goodman, a law professor at New York University and a former special counsel at the US Department of Defense during the Obama administration, says this is the “clearest case” so far of possible crimes being investigated by Robert Mueller, who is leading the federal probe to determine whether the Trump campaign colluded with Russian officials during the US election campaign.

Will Jared Kushner and Paul Manafort be in trouble for attending the meeting, too?

In his original statement, Trump Jr. said he didn’t tell Kushner and Manafort “what the meeting was about.” In the emails, he tells the intermediary that Kushner (brother-in-law to Trump Jr.) and Manafort (Trump’s former campaign chairman) are “likely” to sit in on the meeting, too. Either way, we have no evidence that Kushner and Manafort directly solicited the information.

But Kushner could face a different set of problems, since he only recently acknowledged the meeting in his security forms—even then without fully disclosing its contents, according to the New York Times. Goodman (he uses the Twitter handle @rgoodlaw) says it’s a federal crime to provide false information on these forms, “and that includes omission.”

All this, he suggests, would give special prosecutor enough to “hold over Kushner’s head.”