In The Name of Allaah, The Most Merciful, The Bestower of Mercy
Imaam Ash-Shaatibee [rahimahullaah] stated in Al-Muwaafaqaat that Customs are many different types- some are sound and others are corrupt. The sound customs are those that neither oppose the Sharee’ah texts nor lead to losing an affair deem to be beneficial by the Sharee’ah, nor lead to an affair which the Sharee’ah deems to be corrupt.
As for the corrupt customs, they are those that oppose the evidences in the Sharee’ah or some of the principles of the Sharee’ah, such as some of the customary dealings in usury, and those deeds deemed to be evil by the Sharee’ah which the people engage in during occasions of happiness (or rejoicing etc) [Al-Muwaafaqaat 2/283. Paraphrased & abridged]
NB: Whenever we are unsure whether a certain custom of our nation, tribe or clam is permissible or not, we should seek clarification from the people of knowledge.