In Selectors Level 3, the answer would be NO. The :not() notation accepts only simple selectors.
6.6.7. The negation
pseudo-class
The negation pseudo-class, :not(X), is a functional notation taking
a simple selector (excluding the negation pseudo-class itself) as an
argument. It represents an element that is not represented by its
argument.
What is a simple selector?
From selector syntax:
A simple selector is either a type selector, universal selector, attribute selector, class selector, ID selector, or pseudo-class.
Nothing about a descendant selector.
HOWEVER, in Selectors Level 4, :not() accepts complex selectors, which would include descendant combinators. Browser support is still quite weak for this specification.
