Ruling weakening Voting Rights Act opens door to more states redrawing maps, diluting voting power of minority groups.
Ruling, called 'big win' by Trump, will result in redistricting in Louisiana, but it will have farther-reaching effects.
The state is the latest to act in a national redistricting war that could shape what political party controls the US House of Representatives.
Florida has become latest state to redraw map, as national electoral landscape transforms before midterm elections.
Ruling seen as major blow to US Voting Rights Act, with critics saying it could dilute minority voting power.
Trump’s comments came after the Virginia measure passed by a slim margy of 51.4 in favour and 48.5 against.
This vote is part of a wider national fight between Democrats and Republicans over gerrymandering.
The new maps in Virginia could make it easier for Democrats to take control of the US House of Representatives in November.
The race is tight, and a win could result in more seats in Congress for the Democrats.