Imagine the following scenario:
It is Friday night and I stop by the wine store to pick up a nice bottle for dinner with my beautiful bride. I get to the register, present my credit card and the transaction is rejected. The clerk tells me "Sorry, the Surgeon General has determined that an adult male should have no more than 7 drinks in a week. Government records show that you bought a six pack of beer last Sunday, and of course we assume that some of the 1.5 L bottle of rum you bought at the beginning of the month is still around. You'll have to wait a few days."
or
I pick up a box of condoms at the CVS. The checkout counter rejects me and the clerk tells me "The government has no record of any marriage. You shouldn't be having sex before then. Come back when you've got a spouse."
or
a certain personage gains political power and decides to go all Lucius Cornelius Sulla on his political opponents, so they don't threaten him in the future. You are one of them. Now you can't buy food, medicine, gas for the car, electricity for the house, or anything else. You wait at home in the dark until they come to carry out the proscription.