In the US, IQ tests are not illegal per se, but they're considered difficult to justify. The courts have adopted a disparate impact criteria -- anything with disparate impact requires a justification. Unfortunate as it is, some minority groups score lower on IQ tests, and it's up to the employer to justify whatever cutoff they choose to use. If you use a cutoff of 115, and someone comes along with a 114, it'll be difficult to argue before a judge that the additional IQ point was not just better for job performance, but necessary. As this applies to any number you pick, there's a certain slippery slope to IQ testing candidates at all.
In contrast, a degree in a relevant field is a very yes/no answer, even if the disparate impact is greater.
Not the poster, but as some IQ tests have been proven to discriminate against protected classes, this may be an opening for a discrimination lawsuit. Effectiveness of the lawsuit might vary from state to state. IANAL.
