I'd say all the things that can block/dodge Amaterasu can block/dodge kamui. However we've never seen somebody attempt to block it, so we don't know if it would just go through the barrier or warp the barrier. My guess is it'd warp the barrier. Just like how Amaterasu burns the barrier.
Obito's version seems to be one that can only be dodged, not blocked. I think if obito grabbed Ay, Ay could knock his hand away before he finished and gtfo. But we don't fully understand how obito's side works, so it's merely speculation.