This bill, known as the "Safeguarding the Use of the National Guard Act" or "SUN Act," establishes new requirements for congressional oversight when the President deploys or uses members of the reserve components of the Armed Forces domestically. Specifically, within 15 days of such a deployment, the President must submit a comprehensive report to Congress. This report must detail the precise legal basis and goals for the deployment, including any evidence supporting the assessment, and describe its effect on the identified situation. It also requires information on interactions between military personnel and civilians, along with reports from local and state law enforcement agencies regarding the propriety of the military's involvement. Furthermore, the President's report must identify the total cost of the deployment to the federal government, encompassing indirect costs borne by the Department of Defense and National Guard members. A crucial component is a certification that the domestic use will not hinder the Armed Forces' ability to respond to potential disasters covered by the Stafford Act. Concurrently, the Chief of the National Guard Bureau is mandated to provide Congress with a briefing assessing whether the deployment effectively reduced violence and achieved the President's stated objectives. These oversight provisions, however, do not apply to deployments made in response to natural disasters or weather-related events under the Stafford Act.