You would be in serious trouble if you got caught, but in most cases, the owner of the lawn in question was not too quick on their feet, and could be evaded with little effort.
Well, whipper snapper, keep your running shoes laced tightly, because the old folks chasing you off of their lawn have a new secret weapon: the Inflatable Zimmer Frame walker..Inflatable Costume Walker "Hey, you kids, get off my lawn!" If you’ve ever heard this before, then you were somewhere you clearly shouldn't have been. This has been saving many lawn-trespassers for decades, but if it ever changes, there's no telling how many kids it would cause to have to walk a few extra feet around a yard, rather than straight through it.