The law could simply say employees must only consider things the applicants have submitted themselves. I can think of a few reasons for such a law - applicants

The law could simply say employees must only consider things the applicants have submitted themselves. I can think of a few reasons for such a law - applicants have no control over the internet (eg if I share my name with some criminal who turns up when my interviewer googles me), and this makes it harder for employees to discriminate based on protected categories (race, sex, marital status etc). But as the other replies have said, it's not illegal today.