to make it possible for something to happen The court's decision could open the floodgates for large numbers of other cases involving war crimes.
Usage notes: usually used to describe activities that had been difficult or illegal but which are now easier or allowed and expected to be done by many
Etymology: based on the literal meaning of open the floodgates(to allow water that had been held back to flow freely)
if an action or a decision opens the floodgates, it allows something to happen a lot or allows many people to do something that was not previously allowed (often + to ) If they win their case it could open the floodgates to others with similar compensation claims.