From the Introduction: "Requirements for military awards and decorations can change over time. New events and changes in military, political, or social conditions can generate debate over who is eligible for various military awards. These changes tend to be controversial, especially with veterans groups. Congress has considered several pieces of legislation that would change who would be eligible to receive the Purple Heart, and under what conditions. [...] Congressional offices often receive questions about Purple Heart eligibility from constituents, especially when eligibility rules change. The number of these questions is likely to increase as servicemembers return from conflicts around the world and if eligibility requirements are again changed. This report will examine the history of the Purple Heart and changes in eligibility over time as well as current issues facing Congress."
CRS Report for Congress, R42704
Congressional Research Service: https://crsreports.congress.gov/