Every random number generator (RNG) that is legally used by any casino is thoroughly tested to comply with regulatory standards. Every RNG that has been tested will be then be licensed within the North American gambling jurisdictions covered by that licensing agency. There are other rules and regulations that cover RNG's that ought to be complied with for it to perform up to standard.
State laws will usually require an RNG to perform by a certain standard. Part of the standard enforced by these laws includes a certain minimum win frequency out of all the money put into the machine. For example, the gaming laws of Nevada would require that a slot machine should have a payback of 75 percent. New Jersey law on the other hand requires the payback set at 83 percent. Other states and territories will require almost the same strict guidelines if not stricter ones.
Another important regulation is that a casino can't just simply choose to replace the RNG they are currently using. Before a casino can replace the RNG of any machine or program they're using for their games they offer the casino should first apply for that replacement. When a replacement is granted when the gaming machine is opened it will be supervised by the regulating agency.
In supervising the replacement of the RNG program or chip, it is the representative of the state's regulating agency who breaks the seal on the machine's processor. A new seal is then made on the replacement chip and the gaming machine is then re-certified. That machine's record on the agency's database is then updated and all the information will be maintained. Part of the information stored on the database will the payment percentage thus the RNG for that machine will be tracked and numbered.
Of course, every state will have different rules and a regulation governing the use and operation of RNG's as they are put to use in casinos both on the Internet and offline. An example of such variation of rules will be that certain states will allow the casino to replace the RNG without having to notify any regulating body. The only control set therein is that casinos in the territory can only use state-approved chips. Other rules may include making paper trails.
To make sure every RNG performs according to standard periodic random inspections will be performed on all of the casino's machines. This routine check is usually done by an inspector (or representative) from the state's gaming commission or gaming enforcement division.
Every random number generator used by casinos will be inspected regularly and should perform within standards set by the state or territory. You can be sure that if you walk in a casino and play your favorite machine that it has been checked to ensure fair play.