Can you paint high gloss acrylic over high gloss acrylic without sanding it?

It is never a good idea to paint anything high gloss without sanding first. You don't need to sand clear though the old paint, but the new paint needs something to hold onto. If there is nothing but a smooth, shiny surface, the new paint will probably run if the surface is not horizontal, and then chip and flake very early on. Always run a piece of sandpaper or a sanding block, 150 grit is good, over the surface. Why do something twice?