This Xherdan Shaqiri goal shouldn’t be possible or legal

What Xherdan Shaqiri does here should be illegal.

Whenever anyone tries a shot like this, one of three things happens.

1. It goes straight up, than straight down.
2. It goes right into the keeper.
3. It goes over the bar.

But this one floats and then drops in. And he took it on the run, first time. How can anyone do that?