From the European Court of Justice:
Nº 99/2019 : 29 July 2019The operator of a website that features a Facebook ‘Like’ button can be a controller jointly with Facebook in respect of the collection and transmission to Facebook of the personal data of visitors to its website.
The court’s press release appears below, but the short version of this ruling is that if you have a LIKE button on your web site that would send data to Facebook, you have obligations under GDPR with respect to collecting and transmitting data. The full text of the ruling should be available today from this link.
This ruling may result in many sites deleting the LIKE button. Which would be a good thing for privacy, but a not-good thing for Facebook or for businesses trying to attract a following.