While I share this individual's frustration with the Obama Administration's lack of transparency, I am not sure this phrasing quite works
“There is no precedent for President Obama’s Nixonian assertion of executive privilege over these ordinary government agency records,” said Judicial Watch President Tom Fitton in a written statement.
If the assertion is "Nixonian", doesn't that imply that there is indeed a precedent? Otherwise how would the practice be named after someone else?
PS- since we were on the subject of grammar and editing yesterday, I will say that yes, I know the comma after "Nixonian" above is supposed to be inside the quotes. But as an engineer and former programmer, this rule is entirely illogical. It's like writing 3+(x+y*)7 instead of 3+(x+y)*7. I do it the way that makes logical sense.