Article I, Section 8, of the Constitution, which enumerates the powers of Congress and provides Congress with the authority to make all laws necessary and proper to carry them out; also referred to as the elastic clause.
There is an exact numerical answer to this question. By definition, 1 light year is exactly 9,460,730,472,580,800 meters. By definition, 1 mile is exactly 1,609.344 meters. So, 1 light year is exactly 5,878,625,373,183 and 849/1397 miles, by definition.
You can view more details on each measurement unit: miles or light year. The SI base unit for length is the metre. 1 metre is equal to 0.000621371192237 miles, or 1.05700083402E-16 light year. Note that rounding errors may occur, so always check the results. Use this page to learn how to convert between miles and light years. Type in your own numbers in the form to convert the units!