Raise prices. How would you even keep track of a per customer cap? And higher prices help ensure resources go to where they're needed most, rather than letting everyone hoard up to their cap (some people need little to no fuel). 

 Besides, how do you determine the proper quota in a disaster scenario? Freely moving prices based on incentives are the best way to coordinate markets. 

 Force customers to use digital ID if they want gas.  lol