It's simple: Most of Washington doesn't want him to. To coin a phrase: If they want the president to do it, that means it's legal.The allusion is to the famous Nixon quote (which was distorted for effect in ads for the movie "Frost/Nixon"): "When the President does it, that means it is not illegal." Why would Weigel repurpose that quote? Is he criticizing Obama? Nixon asserted that "in war time, a president does have certain extraordinary powers which would make acts that would otherwise be unlawful, lawful if undertaken for the purpose of preserving the nation and the Constitution, which is essential for the rights we’re all talking about."
Does anyone argue that attacking Libya is needed to preserve the United States? But quite aside from that, Nixon was talking about the President stepping up and doing what he thinks is needed. That's entirely different from saying that a structural safeguard entrusted to Congress may be dispensed with whenever Congress doesn't feel like taking responsibility.
Now, possibly Weigel is thinking everyone knows Nixon was wrong — false, but let's assume it — and so presenting a theory in the Nixon format is a way of saying it's wrong. But I think that's way too subtle for Weigel to have intended. I think what he meant was to adopt a political pragmatism, which he imagines Nixon to have used. In that view, the President acquires power when Congress avoids its responsibility. Weigel continues in this vein [quoting Lindsey Graham, with apparent approbation]:
"I don't believe he needs to come to Congress. I'd gladly vote on what he did. I think it's inherent within the authority of the commander-in-chief to take such action."Such action? What action? Helping out rebels in a foreign country where our national security is not at stake?
"We have been overly cautious, unnervingly indecisive. This thing melted down. I wish we would have acted sooner. I don't feel a need to bless this action before he took it. I'd be glad to vote on it afterwards."Bless? Glad? It's not about your feelings or Congress's avoidance of formal gestures. Either there is a serious constitutional safeguard here or there is not. If there is, it doesn't disappear because you are comfortable without it or because Congress holds back. If there is a constitutional safeguard, it is a permanent guarantee that goes to us, the people.