Frank FMH has given an excellent explanation.
I would just like to point out again that the "es", while not being mandatory, should be included in the sentence for the sake of good style.
1. If you include the "es", the reader, when having read the word "verbietet", immediately knows that
- "das" is the subject of the sentence,
- "es" is an object in the accusative case,
- "Unternehmen" must be an object in the dative case, and
- that there will be an infinitive clause that explains what the "es" means, i.e. that explains what has been "verboten".
This makes the structure of the sentence very transparent.
2. If you leave out the "es", the reader, when coming to the word "verbietet", is unsure about the structure of the sentence.
"Unternehmen" could be an object in the accusative case, and it is unclear what type of information might follow in the subordinate clause.
Only after having reached the end of the entire sentence, the reader will understand that
(a) he/she has just read an infinitive clause that must be taking the place of an object in the accusative case and, therefore,
(b) "Unternehmen" must be an object in the dative case.
Clearly, this makes the sentence much more difficult to understand.
So the sentence is not only correct, but also written in good style.