A direct answer to that question seems to be all over the place. Some articles say it would be up to the Justice Department to make that move. Some say it’s out of the president’s hands. Personally I would say from previous reading that a president would only be able to fire one for “cause”. Like I replied to another poster, we see “cause” when it comes to Comey but would the law? Freepers may be keeping search engines busy on this question as several I’ve gone to aren’t responding!!
The Congressional Research Service is the research arm of congress and its reports are considered to be authoritative. They provided a good analysis of the issue. I’ll see if I can find my earlier post about it and send it to you.
And yes, there is precedent for replacing the FBI Director prior to expiration of his term.
Here’s the post I was referring to. The link to the full CRS report is at the bottom.
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The Congressional Research Service noted in a 2014 report that “There are no statutory conditions on the President’s authority to remove the FBI Director.” More specifically, it stated the following:
“Accordingly, the principles discussed above establish that the President may remove the Director of the FBI at will, given that the “power of removal [is] incident to the power to remove.” Indeed, President Bill Clinton exercised this removal power on July 19, 1993, by firing FBI
Director William S. Sessions. In particular, upon receiving a recommendation from Attorney General Janet Reno that Sessions be removed, President Clinton informed Sessions: “I am hereby terminating your service as Director of the Federal Bureau of Investigation, effective immediately.”
It should also be noted that during Senate consideration of the 1976 measure, Senators Byrd and Hruska emphasized several times that “there is no limitation on the constitutional power of the President to remove the FBI Director from office within the 10-year term. The Director would be subject to dismissal by the President as are all purely executive officers.”
https://www.fas.org/sgp/crs/misc/R41850.pdf