Islam takes an uncompromising stand in prohibiting intoxicants, regardless of whether the amount is little or much. The Muslim is ordered to stay away from drinking parties or gatherings at which drinks are served. ‘Umar narrated that he heard the Messenger of Allah (peace and blessings be upon him) saying,
“Whoever believes in Allah and the Last Day must not sit at table at which Khamr is consumed.”
While it is the duty of a Muslim to eradicate the evil he sees, if he is unable to do so, he must stay away from it, leaving the place where people are engaged in such things.”
Thus,supposedly one was invited to such wedding keeping in mind that a Muslim is prohibited to sit at a table where alcohol is served. how, to deal with the situation at hand?
As Muslims, we are not allowed to have a wedding ceremony where alcohol is served, and other unlawful activities are done. Alcohol is haram and as such no Muslim can either drink or encourage or promote its consumption in any way.
However, as Muslims we must establish good relations with everyone; but this must not lead us to sanction that which Allah has made haram. With this, one can freely apologize for not attending that wedding ceremony as this will be good and will protect from being led to stay, even for a while, at a place where haram activities are rampant. If there is no way out, then one can attend but only as a show of courtesy without sitting on a table where alcohol is served and without indulging in free-mixing that usually accompanies alcohol in such mixed wedding parties.