The ethics rules governing lawyers are a useful starting point to begin thinking about when one’s personal activities become professional disloyalty.

Even though most jurisdictions require that lawyer representing clients never do anything to prejudice or harm them “during the course of the representation,” a lawyer is nonetheless free to exercise his or her right to devote personal time to causes and enterprises that a client might regard as outright disloyal. A billionaire’s lawyer, for example, is free to contribute time, contributions and op-ed pieces in support of higher taxes on billionaires. But the fact that this is permitted by the professional ethics rules doesn’t settle the matter of whether it is right. My own opinion is that at very least the lawyer working in private against the general interests of a client has an obligation to let the client know about it, just in case that client has a different idea of appropriate loyalty than the bar association and might want to hire a different lawyer.

How far does that duty of loyalty extend in other professions? Cleveland Cavaliers basketball star LeBron James was roundly condemned as disloyal after he showed up at a Cleveland Indians-New York Yankees play-off game wearing a Yankee cap. Many in Cleveland felt that even though the NBA season hadn’t begun, the millions paid to James to anchor a Cleveland franchise and persuade Clevelanders to pay outrageous ticket prices to cheer him on also obligates him to reciprocate by being a Cleveland booster in his leisure time. I don’t agree. I believe it would be good, ethical and admirable for James to show the kind of affection and loyalty for the community (the Indians’ lack of success over the decades is a Cleveland sore spot) that its members show for him. I believe it is needlessly provocative for a Cleveland sports star to be shown on national television wearing an opponent’s fan merchandise in a Cleveland venue. But it is certainly not unethical or disloyal for him to say, do and root for whatever he pleases as long as he discharges his responsibilities on the basketball court.

Stupid, maybe.

Then there is Baltimore Orioles first baseman Kevin Millar, who is currently attracting hate emails from Orioles fans on the Baltimore Sun website. Millar, a key player and personality in the Boston Red Sox improbable 2004 World Championship run, agreed to throw out the first ball in the critical seventh and deciding game of the American League Championship Series this year against Cleveland, and also read the starting line-ups for the Red Sox on television before the game. Many O’s fans regarded Millar’s show of camaraderie with his former team as outright treason. Was he disloyal?

The legal profession’s standards would seem to apply. Millar wasn’t appearing in Fenway Park as a member of the Orioles, and his featured participation in pre-game ceremonies was a celebration of his past exploits with a former team, not a show of disloyalty to his current one. Millar’s contract with the Orioles obligate him to play his hardest to win games, and it is hard to see how a post-season show of support for another team in its battle with a third team is any reflection on his devotion to Baltimore. The key test of a conflict of interest is whether loyalty or duty to another person, objective or organization interferes with one’s ability to serve one’s client. If the Orioles are Millar’s “client,” cheering for the Red Sox after the (perennially disappointing) O’s are through playing for the year seems harmless, and certainly shouldn’t interfere with him winning games for the O’s next season.

And Millar had something that James did not: he had the permission of his “client,” the team. The Red Sox asked permission from the Orioles and got it. Could Millar have ethically thrown out the first ball without the O’s permission? I think so, unless some MLB rule prohibits it. But getting permission was the best way to do it.

Or was it? Reading the Orioles fans’ laments on the Sun website, it seems clear that they sense “an appearance of impropriety.” Some of them don’t trust Millar now, and if Millar’s pro-Sox activities anger the Orioles fan base, he has injured his client…which is disloyal.

Kevin Millar’s conduct is a closer call than that of James, even though James didn’t have permission to root for the Yankees; LeBron doesn’t play baseball, after all. Even though fraternization among players on opposing teams is routine today, a fan’s belief that his team is 100% dedicated to beating the opposition is essential to the integrity of the game. Millar is a professional, and this fan doesn’t doubt that he tries to beat his former team as hard as he tries to beat any other. But it was wholly predictable that many Oriole fans would be annoyed by such a public show of support for division rival from their own player.

He should have said no.