Chip Fat Fuel

Since 2010 it has been legal for diesel engines to be run off chip fat, yet before that it was highly illegal and there were severe penalties for anybody who tried it. Why was it banned by law and what has changed since then to make it OK?
See here for background: http://hpanwo-voice.blogspot.co.uk/2012/12/reckless-electricity-generation-in.html.
And: http://hpanwo-tv.blogspot.co.uk/2012/12/nuclear-fusion-power.html.