Mifsud was on the verge of joining Bristol City in the summer before the deal collapsed at the 11th-hour, while two other moves also fell through last month after the Malta international failed to agree personal terms.
"I am glad it is all behind us for his sake and for our sake. He has gone until the end of the season so I think it is safe to say he will never play for Coventry while I am chairman," Ranson told BBC Radio Warwickshire.
"I have spent more time talking about Michael Mifsud since I have been chairman than any other player."
Mifsud, 27, was signed by former City manager Micky Adams from Norwegian side Lillestrom in January 2007. He scored 23 goals in 95 appearances for the club and will be best remembered for his double at Old Trafford in the 2-0 Carling Cup win over Manchester United last season.