Is it illegal to require a candidate to complete a behavioral assessment as a part of the recruitment process?

It is illegal in the USA as mentioned, but most companies worldwide are now conducting drug tests and screenings as part of the employment process. 

In ME it is used in recruitment process because it reflects some of the behaviors expected from the candidates especially that behavior which suits the job requirements or do not suit. Basically it can predict if the candidate suites or not the job and more you can filter among many applicants.

no its not illegal

Well, it is illegal in some countries and from candidate's point of view, it is unethical. But to my opinion, there is no harm doing this. Because bad hiring ultimately means headaches for co-workers, supervisors, human resources officers and other managers.

Behavioral assessment / personality test can provide insight into whether someone is a good fit for a particular job or not. 

Hi Irina,

Good afternoon. In my opinion, I first thank you for giving me opportunity to answer the question. In my opinion, it is not illegal but can be unethical. Every employer would be keen to know about the candidate behavior, since each employer does investments on the candidate, like money, time which is crucial factor in today's business world, etc. Since, the recruited candidate will go under induction program also they will train them to handle their business software's like BI tool mostly. If the candidate's behavior is not fit as per business standard then employer has to replace with right candidate which will consume time, By knowing the behavior of the candidate it could help to avoid to make wrong decisions. But, I would like to make a note that such assessment are not completed integrated in itself. A prudent candidate can easily bypass such assessments.   

Polygraph tests were no longer able to be used for screening of future employees in the United States due to the Employee Polygraph Protection Act of1988 (EPPA).

It is not Illegal, indeed knowing someone's behaviour who is joining you organization is somehow important !! Checking behaviour by talking to someone while sitting across the table having a cup of coffee is not an offense.

It's illegal in The US and I think it's unethical anywhere in the world.