Malay,
That isn't the case anymore. A wrestler can weigh one weight class above their certified weight. For instance, if I was certified at 125, I could weigh in for a tournament at 130 and wrestle 130. Now that the 2 pound growth allowance is in effect, I could actually weigh 132, and still keep my certification @ 125. The catch is at least half of your competition weigh-ins must be at the weight you are going to compete at regionals to be able to enter that weight class.
Here is a question: who checks the # of weigh-ins per weight class?