[Reamer]

Shakermaker said

'Newcastle can't sack him on those grounds. Barton assaulted a colleague while under contract with Manchester City, not Newcastle.'

So in the cynical world of football, just as Man City wanted to cash in on their 'asset', Newcastle will, no doubt, have wanted to protect their investment. If Barton has given them his guarantee that it was self defence and now has changed his toon (sorry!) and admitted his guilt then they have grounds for sacking him.