My first google hit* on "UCI bans compression wear" brings me to this site
road.cc which writes:
"Socks must be no higher than the mid-point between the ankle and the knee. That's not a sartorial judgment on Bradley Wiggins’ calf-length black socks, but it's designed to ban the use of compression socks ([...]). All other compression clothing is forbidden too - so compression base layers and compression leg warmers, which are made by quite a lot of brands, are out. We're not sure at what point normal leg warmers become compression leg warmers, though"
*) But, hey, google personalizes your search results these days, so no guarantee that it will show up first in your google results too.