Grant voting power only to individuals or to entities which follow the same voting power rules. This recursively enforces the rule. A holding company like that

Grant voting power only to individuals or to entities which follow the same voting power rules. This recursively enforces the rule. A holding company like that would confer at most the same voting power as trading XYZ directly, but most likely strictly less voting power in XYZ. A mutual fund which has only held XYZ for a short time would confer little voting power even to shareholders which have held it the longest.