http://en.wikipedia.org/wiki/Saint_Nicholas
Bishop Nicholas at the First Ecumenical Council . . .
Deciding to address the problem as a matter of the state, Constantine called the First Council of Nicaea which also was the first Ecumenical council in 325. The number of attendees at the Council is uncertain with Eusebius of Caesarea reporting as few as 250 and Athanasius of Alexandria as many as 318. In any case
Nicholas is usually counted among them and was noted as an opponent of Arianism.
A later writer claimed that after Arius had presented his case against Jesus' divinity to the Council, Nicholas hit Arius in the face out of indignation. Nicholas was kicked out of the Council for this offence, and jailed as well. However, according to this account, that night the Virgin Mary appeared in a vision to many of the bishops of the Council, telling them to forgive Nicholas, for he had done it out of love for her Son. They released Nicholas and allowed him back into the process the next day.
The council lasted from May 20 to June 19, 325 and resulted in the declaration of the Nicene Creed and the formal condemnation of Arianism. The books of Arius and his followers were condemned to be burned but the execution of this decision was left at the hands of each bishop for their respective territories. To what point this decision was followed remains uncertain.
Following this apparent victory to his faction Nicholas returned to Myra. He is applauded by later Christian writers for keeping Myra free of Arianism. But the decisions of the council failed to stop the spread of Arianism. In fact the tides soon turned and in his later years Arianism managed to win favour with Constantine. In fact Constantine was baptised by Eusebius of Nicomedia, an Arian bishop who had also attended the council, shortly before his death on May 22, 337. Constantine was succeeded by his three surviving sons: Constantine II of the Roman Empire (reigned 337 - 340), Constantius II (reigned 337 - 361) and Constans (reigned 337 - 350). Constantius originally received the Eastern part of the Empire but the death of his brothers left the entire Empire under his control. During his reign he strongly favoured Arianism by seeking to place Arian bishops in most positions. There is no indication that Nicholas was affected by these policies and he remained in his position till his death. This lack of disturbance by the Arian Emperor has been seen as indicating the strong support Nicholas had gained among the people of his territory. According to this reasoning not even Constantius would risk a possible revolt by removing a popular bishop.