The Laffer curve for people certainly exists at a point (say, a 70% tax rate), but it is silly to state it is applicable now - for real-world evidence, look at the tax receipts under the Bush presidency, or Sam Brownback in Kansas. Laffer is a smart dude, but the Laffer curve is not an authoritative law as much as a rule of thumb that applies in a few, limited situations.

I wouldn't say it's a law - just a formalisation of common sense: You can't raises taxes indefinitely, and the higher the tax rate the greater the lengths people will go to to avoid it.