User blog comment:NydusTemplar/April 1st - Suggested Change to Garen (1 Day Only)/@comment-217.121.187.123-20130117103607/@comment-5088437-20130118010226

And Garen's R, Demacian Justice, deals magic damage.

The only mistake I made was implying the scaling part of Justice dealt physical damage. The wiki states otherwise so I'll amend that post. This is what I get from accepting some word of mouth information from a more experienced player without doing full research.