Yes, what you will create is no different than a standard light fixture intended to be hard wired. Assuming you use the proper strain relief and chaffing protection that a new fixture would provide (ie; reuse from old fixture).
I doubt that the UL listing (or other agency) includes cutting off the plug and hard wiring it into a box. The electric code says all equipment must be used and installed per it's listing. Your homeowners insurance probably insists all wiring comply with the electric code.