بسم الله الرحمن الرحيم
What you have heard regarding the unlawfulness of walimah is totally wrong. Walimah is not haram rather it is valid without any doubt according to one opinion. However, it is better to perform walimah after the spouse meet in privacy.
Allah knows Best!
Darul Uloom Deoband
This answer was collected from the official ifta website of Darul Uloom Deoband in India.