https://arstechnica.com/tech-policy/2020/03/facebook-pulls-trump-campaign-ads-for-fake-census-claims/

Facebook infamously has a broadly laissez-faire policy for political candidates. If you're running for office, you can lie as much as you want in your paid and unpaid content—with one small catch. Anything that lies about voting or the census, such as sharing fake registration links or deliberately spreading incorrect polling dates, is prohibited. Even if it comes directly from the Trump campaign.