There has been a lot of arguments in recent history, but the current answer is located in the Fair Use Act, which in a nutshell states that persons are able to burn, copy, rip, backup, or whatever you would like to describe it, if the user are the owner of the original disc. This includes movies, games, and music and any other kinds of media. In fact, it is recommended that persons rip games, ASAP after buying it. By doing this, you ensures that a replica is available in the event the master is lost, damaged or stolen. Furthermore, the replica can be played instead, while the original is stored away for safe keeping. Bottom line: there is no legal penalty for copying Wii games. The FBI will not show up banging down your door, or penalize you for lots of dough.
There is, however, an issue to address if you wish to find out how to copy Wii games. You will require the use of a software program which will eliminate any copyright licenses. Video game companies put these restrictions on the games, in an attempt to stop you from copying the games and vending or permanently lending the games to pals. They can't do anything to completely prevent this from happening, but they sure can try to make it hard. The restrictions themselves are completely lawful, but eliminating them is equally as lawful. So to assist those persons in the world that do not wish to ruin their originals, software companies have invented programs that can do this relatively quickly, and quite easily as well.
Many of these programs can be found with a quick Google search. A good keyword phrase to start with is simply "how to copy wii games".
Once you've identified some candidate programs that you might want to use, you've still got a few things to think about. First, look at whether it's a reputable site. Do they accept Paypal? Do they look like they've been around for awhile? Second, look up some reviews. Even though the software might do what you want, you need to make certain that it's also very easy to use. Reviews from other people who've tried the program before can tell you whether or not this is the case. Finally, look at their refund policy. Make sure that you can get your money back if you're not completely satisfied. This is why it's always nice to find a product through clickbank or Paypal.
Whichever package you go with, make sure that you back up all of your games to keep them safe. Good luck!