In a big win for Broadcasters, the Supreme Court ruled Wednesday that streaming TV service Aereo violates the US Copyright Act.
The major TV networks were among those who put up a united front and filed suit against Aereo back in 2012.
The companies argued that their signals were being sold illegally by the internet start-up.
Aereo charged a small monthly fee to deliver over the air content to computers and mobile devices.
The company's biggest financial backer has said there is no "Plan B" if the court ruled that it was operating illegally.