Employment/ Administrative
An accepted offer to extend a term of employment became valid only upon the end of the previous employment, and subsequent questionable behavior by the employee therefore permitted the employer to decline to extend employment.
http://www.cafc.uscourts.gov/sites/default/files/opinions-orders/14-3188.Opinion.1-6-2016.1.PDF
Since 2011. An occasional commonplacing of the U.S. Circuit Courts of Appeal.
Neither an authoritative statement of the law nor legal advice. Quick work.