IQ testing in America: not banned
See also this post by greyenlightenment.
There is a widespread (e.g. 1, 2, 3) but false belief that the 1970s supreme court case Griggs v. Duke Power Co., 401 U.S. 424 (1971) resulted in a de facto ban on using IQ (intelligence) or other cognitive testing in employment relations. This is not the case. Here's some semi-recent legal reviews.
Shoenfelt, E. L., & Pedigo, L. C. (2005). A review of court decisions on cognitive ability testing, 1992-2004. Review of Public Personnel Administration, 25(3), 271-287.
General cognitive ability is likely the single best predictor of job performance, although it typically results in race-based adverse impact. The majority of the 22 cognitive ability testing cases in appellate and district courts from 1992 to 2004 involved class action plaintiffs and civil service jobs. Organizations that used professionally developed tests that were validated and that set cutoff scores supported by the validity study fared well in court. The validation study must be conducted according to professional standards, and the results should be used properly when setting cutoff scores. Plaintiffs in cognitive ability test-related lawsuits were likely to be members of minority groups; the majority of cases were race-based claims. Utilizing a consultant to develop and validate selection tests may ensure the appropriate expertise and a professionally developed and validated test; however, it does not alleviate the responsibility of the employer for adverse impact.
Morris, N. H. (2016). A Review of Court Cases Involving Cognitive Ability Testing and Employment Practices: 1992-2015. Thesis.
This review is an extension of a study by Shoenfelt and Pedigo (2005). The purpose of this review is to help form an understanding of how the courts handle cases where an organization has used a cognitive ability test to select employees and consequently faced charges. Cognitive ability testing is the best known predictor of job performance for a wide range of jobs. However, cognitive ability testing also is known to lead organizations to select fewer members of protected groups,such as African Americans, Hispanics, and women. The cases that were reviewed were identified in the LexisNexis database. In order to review the cases, pertinent information was coded by four Industrial-Organizational Psychology graduate students then used the information as categorical data to make comparisons based on the outcome of each case and the conditions that may have led to the outcome.Findings were similar to the Shoenfelt and Pedigo (2005), which is likely due to the low number of new cases that were added to the review. Cases in which the defendant had used a validated test often ruled in favor of the defendant. However, in the six new cases that were discovered, issues such as arbitrary cutoff scores and the presentation of equally valid alternatives played a role in rulings in favor of the plaintiff even in cases with a validated test. The case claims were all race based and all involved tests that were professionally developed.
On top of this, we can of course note that many active companies (e.g. Wonderlic) currently sell such tests and aren't being sued out of existence and neither are their clients in general. This whole thing is an example of what happens when you have too many woke lawyers. They add massive costs to companies doing business since they now have to hire consultants to prepare themselves against possible frivolous delusional equality lawsuits. All of this creates useless bureaucratic jobs that suck in lots of talent. European countries seem to have better laws on this topic, at least, yet.