WASHINGTON, DC.- Donald Trump Jr's confirmation that he met with a Russian government lawyer who promised damaging information about Hillary Clinton came as a surprise to many, but many are puzzled about why it matters.

Politics is depicted as a blood sport where anything goes, including whatever damaging information about your opponent you can find. But in this case, legal experts say there's a law specifically preventing foreign nationals from giving away that dirt.

Attorney and legal analyst James Goodnow says the U.S. law precludes foreign nationals from giving money to political campaigns. But it also prohibits them from giving anything of value.

"So the legal question here," Goodnow said, "is what constitutes something of value? The law has a very liberal reading of that and it's anything that would assist the campaign."

Since damaging information about Clinton would be assisting the Trump campaign, and since campaigns routinely pay high-dollar amounts for opposition research, Trump Jr. could be in trouble, Goodnow said.

That information will eventually end up in the hands of special counsel Robert Mueller, who can decide to file charges. But Goodnow cautions that process is likely to take a long time.