NEW YORK ( TheStreet) -- Barnes & Noble ( BKS) is being attacked yet again by billionaire investor Ronald Burkle. Burkle, through his Yucaipa investment firm, filed a suit against the book retailer regarding its shareholders rights plan, which he deems unfair. Burkle also claimed its directors have breached fiduciary duties. Yucaipa currently owns a 19% stake in Barnes & Noble and, back in February, attempted to raise its stake to 37% without triggering the company's poison pill, which was put in place to prevent a hostile takeover. The poison pill is triggered when any investor tops 20%. The goal was to allow shareholders to hold the same number of shares as the controlling Riggio family. Barnes & Noble rejected this bid. Shares of Barnes & Noble are slipping 2.8% to $20.41 in Thursday trading. -- Reported by Jeanine Poggi in New York. Follow TheStreet.com on Twitter and become a fan on Facebook.