Williams and their new chief engineer are being sued by Nascar team Michael Waltrip Racing (MWR).
MWR are taking legal action against Williams and engineer Mike Coughlan for breach of contract, according to BBC Sport.
Coughlan joined MWR as director of vehicle design in October 2010 but moved to Williams in May 2011. However, he was under contract with MWR until November 2012.
Coughlan joined the Williams set-up after a spell with Ferrari and a troubled period with McLaren, where in 2007 he was caught with 800 confidential documents relating to Ferrari's technical information.
McLaren was fined $100m (£62.4m) and removed from that year's constructors' championship as a result of the 'spy-gate' scandal.
