Originally Posted by GrayJay

Flip the front wheel around so skewer is on the other fork leg. If the misalignment switches sides, then problem is the wheel, dish it correctly. If the misalignment stays the same then the fork it the source. Could be either bent fork blades or (less likely) it might be that the fork dropouts are not level with eachother so the wheel is not aligned perfectly vertical. Also check that the distance between inside of the dropouts is 100mm, this indicate if one of the blades is bent inward or if the other is bent outward. Fork blades can be re-aligned if needed via careful bending. Dropouts opening can be made to be level by filing the low one up to the height of the other (or by partially filling the high opening with braze or metal epoxy for a quick fix).