Recently a man went into a Sephardic synagogue with his Conservative Convert fiance to pray and eat. Upon learning of the woman's status, the Rabbi informed the man that once the marriage is consummated, he would be forbidden from receiving 'Aliyoth and there may be further halakhic repurcussions as time goes on. The Rabbi said that nothing could be done because it was the ruling of Ovadia Yosef as codified in Yalkut Yosef. Does anyone know if this is true and where in the Yalkut Yosef it can be found? And as a second question, does anyone know if it is normative halakha to restrict someone in such ways because of their marital status?
I'm not aware of Rav Ovadiah's responsum. There are different communal standards about this.
While a kohen is married to a divorcee (or non-Jewish woman for that matter), his kohen status is "voided" and will not receive any kohen-specific honors in the synagogue. The Talmud entertains -- and then rejects -- the possibility that a Levite would lose Levite honors if he marries someone illegally.
Rabbi Moshe Feinstein has a responsum about giving synagogue honors to a sinner. The issue is that we are prohibited from validating a sinful behavior. (If necessary you may tell a gangster something vague like "you're an okay guy"; but you may not tell a Jew who is driving on shabbos "what you're doing is okay.") He concludes that giving someone an aliyah or the like is not necessarily commenting on any of his actions, and is therefore not prohibited.
Nonetheless, a community has the right to make a statement about certain actions they feel are beyond the pale. A few hundred years ago, there was a blue-blooded Sephardic Jewish fellow in London whose "heart was stolen" by an Ashkenazic girl named Jochebed Baruch; his Sephardic community decided that he could still attend synagogue, but receive no honors. (Okay, that's an extreme example.)
There are many Sephardic communities that draw a simple line in the sand: wear a kipa or not, keep shabbat or not, we don't judge. But if you officially marry out, that's it. You are shunned.
There is such a thing as a "marriage" with a non-Jew. See Ezra chapters 9-10:
It may well be that it isn't a "marriage" without consummation as kesef and sh'tar don't work.
As was the case in the book of Ezra, or possibly because of his reaction, Rabbis may have put a kind of "cherem" on men who marry out in order to pressure them to "divorce" or send away their wives.