The situation you described represents an example of legislative power as outlined in the U.S. Constitution. Specifically, it showcases Congress exercising its authority to create laws that address the needs and welfare of a specific group—in this case, veterans affected by burn pits. This power is derived from Article I, Section 1 of the Constitution, which states that "All legislative Powers herein granted shall be vested in a Congress of the United States, which shall consist of a Senate and House of Representatives."
Additionally, this situation can also be viewed as an example of public policy and social welfare legislation, where the government acts to provide support and resources for individuals facing health issues due to their service.