On Friday, a federal court panel reaffirmed an earlier decision throwing out Virginia's map of congressional districts, due to unconstitutional racial gerrymandering.

The panel found that one district, the third, was unconstitutionally racially gerrymandered in violation of the Equal Protection Clause. "Individuals in the Third Congressional District whose constitutional rights have been injured by improper racial gerrymandering have suffered significant harm," a two-judge majority of the panel wrote.

Virginia is widely believed to be one of the most gerrymandered states in the country. In 2012, Republican House candidates won just 51 percent of the votes cast in the state — but they ended up winning eight of the state's 11 congressional districts. Here's what the partisan results looked like:

All three Democrats won in 2012 with more than 61 percent of the vote, but most Republicans won with margins in the mid-50s — a classic sign of gerrymandering, indicating that the Democratic-leaning voters were packed into a small number of districts. Two years later, in the GOP landslide elections of 2014, not a single Virginia congressional district changed partisan hands.

However, since the US Constitution doesn't prohibit partisan gerrymandering, that alone didn't lead these judges to toss out Virginia's maps.

Democrats argued that black voters were being unconstitutionally packed into one district to dilute their voting strength

Partisanship in the US, though, is often intertwined with race. If you look on the above map at all the blue in the southeast of the state, that's just one, heavily black district — the third, represented by Bobby Scott (D). In fact, it's the only majority-black district in Virginia — even though about one in five residents are black.

So when state Republicans proposed this map in 2011, Democrats argued that another majority-minority district should have been created, and that black voters were being unconstitutionally packed into the third district to dilute their voting strength. Though the GOP got the map through the narrowly divided state Senate by just one vote the following year, Democrats soon sued. Now these federal judges have agreed with their criticism.

The panel of judges has ordered Virginia's legislature to pass a new map by September 1, 2015. The GOP legislature would still draw up the new maps, which could limit hopes of Democratic gains. But the Republican governor who signed the original maps, Bob McDonnell, is no longer in office (and has since been convicted on corruption charges and sentenced to jail time). So Gov. Terry McAuliffe, a Democrat, would be able to veto any new map.