This goes back to the Constitution itself. Article II begins by vesting “the executive power in a president of the United States.” But it doesn’t define the “executive power” anywhere. As the great legal scholar Edward Corwin commented, Article II is “the most loosely drawn chapter of the Constitution. To those who think a constitution ought to settle everything beforehand it should be a nightmare.” By the 1790s proponents of greater presidential authority such as Alexander Hamilton were already arguing “the difficulty of a complete and perfect specification of all the cases of Executive authority” and that “the Executive Power of the Nation is…subject only to the exceptions and qualifications which are expressed in the instrument.” (For instance, that appointees must receive Senate confirmation or treaties ratification.) Whereas Congress’s powers were limited to those “herein granted” by the rest of Article I, the lack of such a restriction in Article II, Hamilton (and later presidents) argued, meant that the specific authorities listed were only examples of the larger whole. In short, executive powers were potentially unbounded.
Vagueness in statute likewise gives presidents flexibility that they tend to interpret in their own favor. Consider two statutes from the “resurgence regime” of the 1970s that were supposed to rein in presidential discretion. The War Powers Resolution, for example, says its very “purpose” is to “insure that the collective judgement of both the Congress and the President will apply to the introduction of United States Armed Forces into hostilities…” Yet it only requires that the president consult with Congress before forces are introduced “in every possible instance.” Presidents have become masters of finding most such instances simply impossible.
The 1974 Hughes-Ryan Amendment and the subsequent Intelligence Oversight Acts, likewise, were aimed at making sure Congress was kept “fully and currently informed” of covert operations and “intelligence activity” generally, including “any significant anticipated intelligence activity.” If the president did not manage to anticipate, he still had to provide briefings in a “timely fashion.” But by 1986, even as the Iran-Contra scandal broke, the Justice Department argued that this phrase should be read to “leave the president with virtually unfettered discretion.” Amendments to the act in 1991 required presidential findings authorizing covert actions to be pro- rather than retroactive, at least; but they failed to overcome a presidential veto threat and thus did not add a statutory time within which Congress had to be notified of what was going on.
President Obama’s NSA speech seems very much of this lineage. Indeed, he was careful in discussing past communications with lawmakers to merely say “we’ve sought to keep Congress continually updated on these activities.” (Is it his fault if his seeking does not find?) And when it came to specific proposals, most had the potential to be change current policy — but came with key qualifiers. For example, the store of metadata, whomever winds up keeping it, should only be queried with judicial permission — “or in the case of a true emergency.” Foreign leaders should not be wiretapped — “unless there is a compelling national security purpose.” Some sort of independent panel of public advocates from outside government should work with the FISA court — on “significant cases.” Personal information (says the related Presidential Policy Directive (PPD-28), here) “Personal information shall be disseminated only if the dissemination of comparable information concerning U.S. persons would be permitted under section 2.3 of Executive Order 12333,” but as Benjamin Wittes points out on Lawfare, that section “include[s] just about any reason an intelligence agency might legitimately want to disseminate material.”
Now, there are good reasons for not “settling everything beforehand.” And we shouldn’t expect presidents to volunteer to tie their own hands. The problem is that in recent years we haven’t been able to expect Congress to do so either, or at least to make a serious effort to establish a working balance between pragmatism and presidentialism. Indeed, Peter Hoekstra, who used to chair the House Intelligence Committee, recently predicted that “you will see changes at the margins with significant ambiguities and exceptions that will provide the executive branch with lots of flexibility.” That will be just fine with President Obama, and with his successors.