The "next sentence" does not undermine the argument.  The issue is whether Article II, Section 2 of the Constitution grants the President the power to conduct warrantless wiretaps of foreign intel national security information, the question specifically reserved in Keith.  Your argument that "without FISA laws the President actually has LESS power" is flatly wrong:  If the Administration is correct, then Congress could not by statute eliminate this power, nor could a President by signing legislation relinquish such power--otherwise mere statutes could "amend" the Constitution (see the discussion here).

The "next sentence" is relevant to the authority of the case.  Yet, regardless of whether the discussion in In re Sealed Case (slip op. at 48) was dicta (a 2000 case from the Southern District of New York includes similar language, United States v. Bin Laden, 126 F. Supp. 2d 256, 264 (S.D.N.Y. 2000)), it quoted the Truong case, 629 F.2d 908 (4th Cir. 1980), which in turn correctly characterized all court of appeals cases to that date as having affirmed Presidential power under Article II.   Many of those cases are cited and quoted here.)  Yes Truong and the cases it cites were pre-FISA, but again, if the President is correct that Article II supplies the authority, FISA could not alter that.

Again, please deal with the actual argument.