Just and Unifying Solutions To Invigorate Communities Everywhere Act of 2021 or the JUSTICE Act This bill addresses policies and issues regarding policing practices and law enforcement accountability. The bill funds state and local grants, incentivizes state and local reporting on the use of certain policing practices, creates new federal offenses for certain misconduct, and establishes best practices and training requirements. The bill funds state and local grants, including to support the use of body-worn cameras, to implement information sharing systems for disciplinary records of law enforcement officers, and to prohibit officers from engaging in sexual acts under color of the law. Further, it requires state and local governments that receive grants under the Edward Byrne Memorial Justice Assistance Grant program to report information related to use-of-force incidents and the use of no-knock warrants. At the federal level, the bill establishes new criminal offenses related to falsifying police reports and engaging in sexual acts under color of law. The bill directs the Department of Justice to develop training on de-escalation tactics, behavioral health crises, alternatives to the use of force, and the duty to intervene when another officer uses excessive force. Finally, the bill establishes and funds the National Criminal Justice Commission. Among other tasks, the commission must develop best practices for policing tactics and procedures.