does President Trump have any legal requirement to hand over business documents mueller asks for??? can’t he tell mueller to go F himself should mueller demand certain business docs?
The conduct of investigators is examined "post," meaning they can do whatever they want, and challenges come after. The target of an investigation is not the one producing evidence. In this case, evidence is being demanded of other government agencies (IRS), banks, phone companies, and so on. Those entities won't object to a subpoena or order from an investigator.
So, the principle is that the investigator has a duty to limit his search. They are forbidden from going on fishing expeditions, see 4th amendment and probable cause and related doctrines.
Mueller is further cabined, in principle, and it is incumbent on HIM to obtain approval to expand his jurisdiction. The approval would come from Rosenstein.
Based on the news reports, at least Mueller is stepping outside of his jurisdiction. Whether or not this is with Rosenstein's blessing has not been reported. Mueller is cabined to conclude the investigations described by Comey in his March 20 testimony, and that limit is the conduct of the election campaign. He is not supposed to step outside of the election campaign. Any events prior to startup of the election campaign can't be related to the election campaign.