User blog comment:SoKoLoV/New Interview with Todd Howard and New Information & Footage/@comment-76.17.24.174-20111024000123/@comment-4317122-20111024072428

You can block with a one handed weapon as long as you have nothing equiped in your other hand and you can block with a two handed weapon. Blocking this way is not as effective as using a shied to block. You can not block while dual weilding.