I don’t think so - he’s either an apostate or crypto-Catholic (as Muslim women can not marry non-Muslim men, so, at best, he was lukewarm to give his faith up for a woman), and the Sacraments are one-time-only deals, as they leave an indelible mark on the soul (e.g. they can not be repeated in any circumstance that it is known they were properly administered before; this was settled over a thousand years ago as part of the Donatist controversy). Islam is incredibly easy to convert to (all one has to do is speak a single sentence in Arabic) - and incredibly hard to leave (like the Hotel California) - but I don’t believe the conversion counts if one says it without intent (I have said it many times to Muslims to prove it has no magical quality); however, to say it for convenience or for a woman, and not to avoid persecution, seems to me like it would be a severe mortal sin, unlike in periods of severe persecution, where one might convert with the lips but remain fully Catholic in practice.
I don’t know how he’d go about rejoining communion with the Church, as he’s been excommunicated latae sententiae, but one would have to ask a priest. According to the religious law of Islam, if he would convert out of Islam, his marriage is automatically annulled, he forfeits his children and property, and in states with a more thorough application of Islamic law, his life.
I think it is imperative to bring a priest in to the situation immediately, at the cost of your friend’s immortal soul, and his earthly life as well, so, if his wife is a practicing Muslim, he doesn’t fall bit by bit in to practice of that most unholy religion over time, i.e. by fasting Ramadhan one year, and then taking part in the Jumuah prayers, and then becoming a full-blown Muslim.
