We disagree. And so do definitions at Cambridge University Press – and other major publishers.
They seem to be confusing the definition of the word “nullification” with the definition of the word “obstruction.”
While obstructing federal agents could certainly have the effect of nullifying a federal act, it’s not always the right strategy, and it’s certainly not the only strategy.
Taking other actions – such as refusing to enforce or participate can, as Cambridge says, “cause something to have no value or effect”
And that’s our end goal on all unconstitutional acts.
On the other hand, who cares what you call it if the end result is the same?