Since the release of Effect Veiler, this is a question that has been asked again and again. Can Chaos Sorcerer/BLS attack if their effect is negated by Effect Veiler? And most people who know the answer, they just memorize: "effect veiler=Chaos can't attack" without knowing why. So this issue rises 2 questions. Before analyzing them, let's take a look on the part of their text about not attacking:
"This card cannot attack during the turn you activate this effect."
Q1: "Why can't I attack since the effect is negated?"
The answer here (as in many ruling issues in YGO) lies in the difference between activating the effect and resolving the effect. Effect Veiler does not negate activations of Monster Effects (same as skill drain). It only causes them to resolve without effect. The fact that you didn't resolve the effect doesn't mean you didn't activate it. And since you did, according to the text, you cannot attack that turn.
Q2: Isn't the above text also negated by effect veiler? So, shouldn't I be able to attack?
The answer is that the above text is NOT part of an effect of Chaos Sorcerer, so Veiler can't affect it. It's just a condition, and barely anything in the game can affect such conditions/maintenance costs etc...
"This card cannot attack during the turn you activate this effect."
Q1: "Why can't I attack since the effect is negated?"
The answer here (as in many ruling issues in YGO) lies in the difference between activating the effect and resolving the effect. Effect Veiler does not negate activations of Monster Effects (same as skill drain). It only causes them to resolve without effect. The fact that you didn't resolve the effect doesn't mean you didn't activate it. And since you did, according to the text, you cannot attack that turn.
Q2: Isn't the above text also negated by effect veiler? So, shouldn't I be able to attack?
The answer is that the above text is NOT part of an effect of Chaos Sorcerer, so Veiler can't affect it. It's just a condition, and barely anything in the game can affect such conditions/maintenance costs etc...