The Evil GM - "I'm the DM, My Campaign, My Rules."

DM Fiat, we've all experienced a game where the person running it changes the rules to fit the situation at hand. Maybe you don't care much about it as long as the game is fun or maybe it drives you up the wall to the fact you've moved on from playing with that DM.

Either case, does the DM have the right to say, "Well this is my campaign, so we are going to follow these rules."

You look over these rules and he is restricting various classes, races and even alignments. Examples of this would be: 

• No Evil or Chaotic Neutral aligned characters.

• The following class is not allowed

• Background type is not allowed.

• Certain skills can not be used

• Certain spells are not allowed

• Whatever other rule is not allowed here.

I've done some of these things in my campaigns, but I explained to my group why these things are not allowed, and the option of not playing that game was always on the table, with no hard feelings. No player has ever said, "No I am not playing."

Everyone seemed to agree and was okay with the adjustments.

But is it truly okay for a DM to remove things that come standard in the rules?

I know most people will argue that if its in the main core rule book of whatever edition your group plays, its considered valid and can be played!

So does the DM have the right to strip things out of the game to fit his campaign world? Does this unbalance the game or its fine as long as its not too much, its fun and the group agrees to it?

Thoughts?