(Reuters) - Additional permanent concussion substitutions will be enshrined in football's laws but it remains an option which is up to organisers of individual competitions to implement, the International Football Association Board (IFAB) said on Saturday.

Soccer's law-making body IFAB held its annual general meeting in Loch Lomond, Scotland where they also said trials for using sin bins as a punishment for dissent and tactical offences will continue to be refined.