Gee, I was hoping for a cool video about chainguard removal. Anyway, many guards are held on by the BB nut - yours is one of 'em.

I doubt that a manufacturer would have made a guard that prevents crankset removal, chain replacement, BB replacement, etc. It appears to have a seam or joint running around its outer edge. If there are no bolts, the inner and outer halves probably just snap together. You should be able to gently pry them apart. If they are stuck, apply penetrating oil around the seam. Then, remove the crank and chainring. With the chainring and outer guard off, you can unfasten the BB nut.