Per a story covered in various media outlets, the March for Our Lives was prevented from being on the National Mall by a “small student grout filming a talent show“. As far as I know, this group was never identified. The march was held anyway, and indeed, considering how sloppy the Mall would be after snow melt, it probably for the best. They weren’t up to their knees in mud.
However, despite calls for this student group to identify themselves and to relinquish the National Mall for a far far more important issue, there seems to be nothing. I hope someone can fill in the blanks for this, rather than having to go through a Freedom Of Information Act (FOIA) request.