Why is there a limit on intercepts of enemy communications?

NY Times:

The National Security Agency intercepted private e-mail messages and phone calls of Americans in recent months on a scale that went beyond the broad legal limits established by Congress last year, according to government officials.

Several intelligence officials, as well as lawyers briefed about the matter, said the N.S.A. had been engaged in “over-collection” of domestic communications of Americans. They described the practice as significant and systemic, although one official said it was believed to be unintentional.

The N.S.A. legal and operational issues have come under scrutiny from the Obama administration, congressional intelligence committees, and a secret national security court, said the intelligence officials, who were speaking only on condition of anonymity because N.S.A. activities are classified. A series of classified government briefings have been held in recent weeks in response to a brewing controversy that some officials worry could damage the credibility of legitimate intelligence-gathering efforts.

The Justice Department, in response to inquiries from The New York Times, acknowledged in a statement Wednesday night that there had been problems with the N.S.A. surveillance operation but that they had been resolved.

As part of a periodic review of the agency’s activities, the department “detected issues that raised concerns,” the statement said. Justice officials then “took comprehensive steps to correct the situation and bring the program into compliance” with both the law and court orders, the statement said. It added that Attorney General Eric H. Holder went to the national security court to seek a renewal of the surveillance program only after new safeguards were put in place.

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Is this story suggesting that the NSA can only intercept a limited number of enemy communications with Americans? What sense does that make. It sounds like a lottery in which if we get lucky we will intercept the attack order, but if we get unlucky the NSA will not be allowed to look at a message that may be an attack order.

Why would an important national security operation be structured in that way and why would the AG not be seeking to get the law changed rather than bow to a ridiculous restriction on intelligence gathering?

The liberals attitude of protecting terrorist privacy rights seems like poor judgment in the extreme.