What is the ruling on weddings in which the bride and groom wear a wedding dress and a suit, and dance in front of people, and how should one deal with those who justify this by saying it is "once in a lifetime"?

The dancing of the bride and groom in front of the attendees in the wedding hall is a reprehensible fitnah (temptation/strife) and intermingling. A man's approval of his wife swaying in front of men is a sign of diathah (pimping/lack of protective jealousy) and an incitement to indecency, especially if she is adorned. This act is forbidden. Similarly, the husband dancing in front of women is not free from fitnah, especially if it is accompanied by forbidden singing and musical instruments. Such weddings are forbidden, and it is not permissible to hold or attend them except for the purpose of enjoining what is right and forbidding what is wrong, for occasions do not alter Sharia rulings. It must be clarified that tying joy at weddings to the violation of prohibitions and the commission of reprehensible acts replaces gratitude for Allah's blessings with His wrath. "No affliction descends except due to a sin, and none is removed except through repentance."