An eternal problem with selling games

One thing I've been thinking about for a while now is how I'm going to go about selling this game. If I make it something that one pays to download, then that person could buy and redistribute the game for a lower price, or even free. The question is: How does one get around that? I'm thinking of making a site, where you can play the game online, without having to download any content onto you computer. I'm not sure if I'm going to have people pay to create an account, or if I'm going to make people pay to buy the game. Regardless, one of the two ideas suggested is likely going to happen.Below is the protagonist, Kyon, in all his epic-ness!

John Smith: Ace Attorney DEMO

I've been thinking about what should make up the demo for a while, and I'm looking towards using the first 2 cases for the demo. This isn't set in stone, but it's what I'm looking towards now. Also, the plot is basicly done for cases 1 and 2 ,(What happens, as well as dialogue) However! I'm just starting with the graphics, as well as the background music. Basicly what I'm saying is, it's going to be a while until this is done...Below is an old version of something I planned for the first case. Enjoy!

A Run-Down of The Game

    To give you a better idea of how this game is set up, you will be playing through five court cases, each case being longer,(and harder) than the last. In these cases you will be able to meet various people involved with the case at hand, and slowly discover the chained pasts that connect all these people together. There will be two parts to each case: One will be in court, battling the prosecution; The other out of court, searching for clues to try to discover the truth of the case. You will be able to decide the fate of each trial. Whether your client is found innocent, or guilty, is up to you!

                          Enjoy this picture of Nagato Yuki!----->