Luatua hit Nanai-Williams with a late, swinging arm off the ball that earned him a red card just before halftime in the Super Rugby clash in Hamilton on Friday night.
A Sanzaar foul play review committee suspended him from all forms of the game up to and including Saturday, April 1.
Luatua had pleaded guilty to dangerous tackling of an opponent.
The committee, headed by Christchurch QC Nigel Hampton, said they had looked at all the available evidence , including all camera angles, and had heard evidence from Luatua and his lawyer before upholding the charge.
