First, we would like to draw your attention to the necessity of observing the limits of Allah and the gravity of incurring His wrath by having any impermissible relation with a woman. The relation between men and woman has been strictly restrained by Islam. Having a feeling of love toward the opposite sex is not allowed unless it becomes a motive to marry her.
Second, if there is an assurance of the personality and religiousness of a woman and the marriage responsibilities can be afforded, then a man has the right to marry her even if his parents do not agree. This is his personal life and his opinion is advisory. However a man should try, as far as he can, to get their approval and consent; but be careful not to transgress the limits of Allah concerning them. Appeal to their affection and mercy to empathize with your emotions.
On the other hand, the marriage contract has to fulfil all its Islamic conditions and requirements including witnesses, wali (woman’s guardian), announcement… etc. The Prophet (peace and blessings be upon him) said: “No marriage is valid without a wali and two just witnesses.”