California’s Supreme Court has ruled that Yelp YELP, -0.10%[1]  can’t be forced to remove a negative review — but that doesn’t mean consumers should trust bad reviews.

Three of the four justices who ruled in favor of Yelp[2] on Monday argued that the Communications Decency Act protected sites like Yelp in cases like these. Previously, a California state appeals court had ruled that Yelp needed to remove libelous reviews written by an unhappy client of a California law firm. The remaining justice who ruled in Yelp’s favor instead argued that Yelp couldn’t be held accountable because it was not a party to the law firm’s original suit.

“Litigation is never a good substitute for customer service and responsiveness, and had the law firm avoided the courtrooms and moved on, it would have saved time and money, and been able to focus more on the cases that truly matter the most — those of its clients,” Aaron Schur, deputy general counsel at Yelp, wrote in a blog post[3].

Also read: Amazon customers are fiercely loyal — and this is why Trump’s tweets won’t change that[4]

Indeed, federal law protects sites like Yelp from being liable for user-created content they publish. But that doesn’t give users free license to post whatever they want. Nor does federal law require that reviews left on sites like Yelp or Amazon AMZN, +0.64%[5] must be accurate. Here are important factors consumers need to consider when it comes to reading — and writing — online reviews.

Writing a bad review can have its consequences

While Yelp escaped scrutiny in this case, the woman who originally left the negative reviews[6] did not. She was compelled to remove them and still owes the law firm monetary damages.

She’s not alone. A New York gynecologist recently sued one of her patients[7] for $1 million over a negative review posted to multiple sites, including Zocdoc and Yelp. And a cattle farmer from Kansas was sued over a TripAdvisor review[8] his family left for a Missouri attraction.

Review sites like Glassdoor [9]and Yelp[10] offer tips on how to write negative reviews in ways that avoid defamation claims and provide guidance on what to do if you get sued over a review. “I would not take the lesson that users cannot say anything they want to say,” said Joseph Reagle, a professor at Northeastern University who studies online communities and reviews.

Users who want to leave reviews should be...

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