And therein is the REAL reason Blue Laws are seldom repealed. The liquor store owners (and similarly the car dealers) realize that if if the law is changed such that liqour can be sold on Sundays, then eventually they will have to be open on Sundays in order to compete, and yet on an annualy basis they won't make any more money by doing so. So they lobby the relevant government entity HEAVILY and/or spend lots of money on negative advertising to keep the Blue Laws in place.
I think they can actually choose Sunday over Saturday, if they want to. I know we have a Dodge dealership that does this, staying closed on Saturday and open Sunday.