Yudhisthira decided to institute a code of conduct after all the brothers marry the princess of Panchala, lest she, became the cause of family’s dissemination. It was decided, when Draupadi was with one of the brothers in her chamber, others would not enter or even caste a covetous look on her. In case of any transgression it would result in banishment for a period of twelve years.
Once some thieves stole a brahmin’s cow. On listening to his plight, Arjun in haste rushed to Draupadi’s chamber to fetch his arms. She was with Yudhisthira.
The duty of a warrior is to help people in distress. Accordingly Arjun had not transgressed any law or rule by storming in Draupadi’s chamber. But a predetermined law had been violated.
Arjun after full consecration rites, left for the forest, to live the life of a celibate for twelve years.
ARJUN MARRIES ULIPI
He spent the days hunting, practising his weapons, offering oblations to deceased ancestors and sporting in Ganges water. During one such moment, he had a close encounters with Ulupi, daughter of a Naga king Kouravya. Ulipi was smitten. She was aware that Arjuna was under vow of celibacy. But the woman was head over heels in love with the handsome warrior. If her love was not reciprocated, she was sure to take her life and die. The thought made Arjuna shudder. He agreed to unite with her lest be burdened by someone’s death. This would taint his soul and would be against Dharma. Arjun spent time with Ulupi in her father’s palace. Finally he took leave.
picture from wikipedia