Do you see how this is pretty much entirely false or irrelevant to the actual argument? 1) you don't have to have the weather war "won" to have sand up for a period of turns. In these instances, while the weather war is being fought, there can easily be sand up, in which sand veil happens. 2) sand stream is a passive effect. Sand being up does not constrain the user's turn. Having to use a specific high secondary chance move, or using scald that turn, or forcing volcarona to be hit by a contact move DO constrain that turn. They force the turn for their effects. Sand veil, or any other evasion ability, does not. 3) the pokemon with sand veil DOESN'T HAVE TO DO ANYTHING. It can do whatever the hell it wants, as the only condition that needs to be met is you attempting to kill it. It can attack while relying on sand veil to escape damage, or use a support move, or set up, or anything, while relying on sand veil. There is nothing they have to do--and can thus do ANYTHING--and that's the problem. I would consider the same for snow veil, but whatever.