Hopefully, most people were going by this rule in the first place. 

WREX - Starting Friday, April 3, Costco will allow no more than two people to enter the warehouse with each membership card.
Costco says the temporary change is for safety and the safety of their employees and other members, and to further assist with our social distancing efforts.

I haven't noticed many large groups when I've been out grocery shopping the last few weeks so hopefully, this is just a reminder and preventative measure, rather than an attempt to correct behavior.

These are the guidelines that we all need to voluntarily follow for a little bit to help us all get through this.

Stay safe out there, we'll be stronger on the other side.