As when a spoiled child has never been punished by his parents, he will therefore continue to misbehave and do wrong.
The closest thing I can think of is the phrase to get out of hand. Even though this expression is mostly used for situations that gradually get out of control to the point where they become utterly chaotic, it can also be used to talk about people and children. The difference between this expression and the expressions offered in the comments section is that this one is definitely an essential part of everyday English vocabulary.
Little Johnny is getting completely out of hand! I think he needs a good old ass whipping.
But on a more conceptual note, the situation where you will misbehave because you know that you won't get punished for your actions is commonly known as acting with impunity.