The French President, Emmanuel Macron, said during his new year press conference he would soon propose laws preventing false information from spreading on the web ("fausses nouvelles", more or less equivalent to "fake news").

Has there been any attempts to do this in the past ?

Other than blasphemy trials of course (religious or not).

To clarify, the hard part would seem to me to be able to decree something to be false. It is quite hard to decide. Propaganda is usually build on either a selected set of true information, or unverifiable stories (plots mostly).

Let us say I see a documentary praising the liberation of Poland from communism by Nazi Germany. They can interview a few Polish people who say they are happy about it, stay vague, even say the economy is doing great. As long as they don't say any number, or false and verifiable fact, it cannot technically be counted as false.

Similarly, let us assume someone on TV speaks about a plot from globalist alien vampires to control the world. As long as I don't have a technique to vet if someone is an alien-vampire, I cannot consider it as false.

The only cases currently covered so far seem to be defamation.