Generally, with the apostrophe, although all of the following are fine. our company's rules the rules of our company our company rules "Rules" is fine but generally we would say "policies" or "regulations", but that is a different topic. I hope that helps.

both, depending on context "Company rules" state that tobacco usage is forbidden. (subject). Our company's rules state..............................................

Both are correct. I prefer “company rules” but would use “company’s rules” if I wanted to emphasize the attachment of the rules to our particular company.