(found by @TalbotG)

css-values-3 (and 4) say that

Properties may restrict numeric values to some range. If the value is outside the allowed range, the declaration is invalid and must be ignored.

However, there is at least one exception: the rgb() function, which says:

Values outside the device gamut should be clipped or mapped into the gamut when the gamut is known

and gives examples of values below 0 or above 255.

So, since there are some cases of properties doing restriction on the range other than at parsing time, we should probably change the sentence in css-values to something like this:

Properties may restrict numeric values to some range. Unless specified otherwise, if the value is outside the allowed range, the declaration is invalid and must be ignored.

This makes it clear which requirement takes precedence instead of just having a contradiction.