That's not quite how it works. In practice, in the US, liability comes not so much from giving a positive or a negative review, but from giving an incomplete one. This is most apparent as a result of giving a positive review and leaving out the bad bits. In this case, you might be liable for the negative consequences of hiring someone based on your positive review.

For an extreme example, see Randi W. v. Muroc Joint Unified School Dist [1]. In that case, the plaintiff sued several school districts for fraudulently or negligently providing positive recommendations for a teacher who ultimately sexually assaulted her. The California state Supreme Court held that the school districts were liable because there was a substantial, foreseeable risk of physical injury to a third-party resulting from the misrepresentations.

For this reason, it is common practice for businesses to decline to provide a review and instead simply confirm a prior employment relationship and the dates of the employment.

[1] https://law.justia.com/cases/california/supreme-court/4th/14...

Personal references are protected, to the extent that liable and slander laws would apply.

Any HR person / lawyer will tell you providing a negative review of an employee, let alone with amount of detail, opens you up to liabilities that aren't worth it.

As an employer, I've been told that, if called, I should only provide the date a person started with the company, the date a person left, their starting and ending salaries (murky now given salary history laws) and whether they'd be eligible to be re-hired.

I ask any employee we fire for cause not to list us as a reference.

Would be more useful if you pointed out which part of the Bill of Rights provides this protection.

which one protects giving negative references