The midfielder has received a lawyer's letter informing him that he will be in breach of contract if he uses his Twitter account to comment on club affairs in future.
Like every other Newcastle player, Barton has been issued with new, strict guidelines for Twitter usage, prohibiting any revelation of "privileged" information that may offer opponents an advantage or undermine colleagues. Potential sanctions include fines, suspensions and, ultimately, sackings.
"The problem I have with this new medium of Twitter is that people are twittering in an emotional state," Alan Pardew, the Newcastle manager, said. "Putting something out instantly can be very, very, damaging. Not only to a football club but to any organisation and it could be to the police too, which I've seen on occasion."
Outraged not only by Barton's tweeted criticisms of the club's spending policy – which led to the 28-year-old being made available on a free transfer – but similar gripes expressed by José Enrique, Newcastle's left-back, via the same medium, Pardew sought counsel from his Manchester United counterpart.
"I spoke to Sir Alex Ferguson, and United's policy is that nobody at their club can comment about the football club [on Twitter]," he said. "It's in breach of contract if you are criticising the owner, the masseur, a player, anyone at the football club ... Giving out injury news, that causes problems too."
Reassured by Ferguson's stance, Pardew consulted the St James' Park lawyers as they put the final touches to a letter distributed to every squad member, similarly restricting their tweeting scope.
"We've notified the players this morning," Newcastle's manager said. "They've probably seen it as another sort of dictatorial moment from us but we've had to issue them legally with a letter to say this is not right, it's a breach of contract and you have to understand you're going to be fined and disciplined for that. It can't happen. Sir Alex shared with me quite ferociously how difficult this Twitter issue is for clubs, particularly managers."
Manchester United are one of number of clubs who have, so far at least, passed up on the opportunity to sign Barton. Though the midfielder may still depart before the transfer deadline, the lack of takers means he and Newcastle may be stuck with each other. "Joey will dictate what happens because he's got another year on his contract here," said Pardew, who was left furious after a show of dissent from Barton at last Sunday's friendly defeat by Leeds. "Joey will decide. But if he wants to stay then he has to pull in the same direction as us. I've made that clear to him and, at the moment, we're in a period of reflection."
This involves time apart from the first-team squad. Barton, who trained alone on Tuesday, worked out with the reserves on Thursday and will play no part in Saturday's friendly at home to Fiorentina.
"Everybody was very angry this week and there were decisions on both sides that were made with that anger still at the surface," Pardew said. "But I cannot and will not run a football team where a player isn't pulling for the team. It was evident that whatever happened with Joey's mind affected the team. I can't accept that."
Pardew concedes the incident has exerted a toll on dressing-room camaraderie. "No, I'm not happy with it," he said. "It hasn't been the most perfect pre-season. I don't think Newcastle United are in chaos but are we having a difficult week? Yes. Do we need to get our fans into a better place? Yes. Does the team need to improve on the pitch? Yes."
He hopes to strengthen his Newcastle side by making a couple of signings. Negotiations are continuing with Bayer Leverkusen for the 26-year-old Switzerland international Tranquillo Barnetta, who excels in Barton's optimal right-wing position.
"The problem I've got with the group at the moment is that they want to see one or two players coming through the door," said Pardew, who confirmed he had received "no bids" for José Enrique. "I'm making it very, very clear to Derek and Mike [Llambias and Ashley, Newcastle's managing director and owner] that we need one or two boys in this door. Now."
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