Kevin and Christopher were stabbed in street clashes in downtown Istanbul the night before Leeds played Galatasaray in a UEFA Cup semi-final in April 2000.
West Yorkshire coroner David Hinchliff said he would write to the English Football Association and European governing body UEFA to recommend the introduction of an international protocol to protect away fans.
In Istanbul, Ali Umit Demir is serving a 15-year prison sentence for the stabbings. The sentence is currently under appeal.
"Turkish nationals were observed charging down the streets, arming themselves with any missiles they could get their hands on and throwing them in the direction of the Leeds fans," Hinchliff said. "It was a pre-planned and orchestrated attack."
Hinchliff also criticized Turkish police as "disorganized, uncoordinated, not in control of the situation and ill-prepared."
"I do not hesitate to regard Kevin Speight and Christopher Loftus as being unlawfully killed," Hinchliff said. "There could have been no justification for their deaths."
The families of both men welcomed the verdict, but lamented that little had been done to prevent further attacks.