Three of the major US TV networks – Fox, NBC and CBS – are suing the maker of a set-top box that lets viewers skip the adverts on shows they've recorded.
The BBC reports that Dish Network, which makes the Hopper set-top box, has filed a separate lawsuit asking that ad-skipping can go ahead.
Dish Network launched its Hopper digital video recorder earlier this year at CES in Las Vegas. On May 10 it added an "auto hop" feature that allows viewers to skip over adverts that interrupt shows they had recorded.
The TV networks are worried that their main source of revenue will dry up if viewers no longer watch the advertisements.
Fox claims that showing a programme without ads amounts to re-broadcasting it – and that violates the agreement Dish has with the broadcaster.