Rihanna, Billie Eilish, Lizzo and Justin Bieber have all backed a major open letter calling for police reform.The US stars have joined forces with record labels such as Sony Music Group, Universal Music Group and Warner Music Group to support Congress’ Justice in Policing Act of 2020.The support, which was also backed by the likes of Mariah Carey, Ariana Grande and Post Malone, follows the death of George Floyd last month.