Here are a number of judgment calls that parents make every day. There are no laws -- just your best, most educated, guess. I'm betting that the range of answers will mirror the "it all depends on everything" reality of parenting.
At a party last week, a couple told us a "funny" parenting story. They were staying in Paris, and decided to leave their 1-year-old asleep in his Pack 'n Play, and get a drink at a place nearby. No need for a babysitter.