A three-year-old claim that Facebook would implement a "no swearing" campaign to create a "family-friendly social-network" -- and would lock or shut down the accounts of offenders -- was revived in a 2017 meme:
The meme was a rehash of a similar March 2014 meme purporting to be a message from Facebook CEO Mark Zuckerberg saying that the move came at the request of advertisers:
Oddly, both memes referred to "new laws issued by [Facebook's] legal department." Though we can't imagine it needs clarifying, Facebook does not have the legal authority to create laws in the United States or anywhere else. Only elected officials and legislative bodies can do so.
Needless to say, Facebook has made no such announcement nor sent any statement about launching an anti-profanity campaign like the one described here. Note that the date of implementation in the 2017 example coincides with April Fools Day.
Facebook does provide optional profanity filters that will block posts containing certain offensive words, and Facebook's Community Standards and Statement of Rights and Responsibilities sets down some guidelines about posts that might be considered hate speech.