50 U.S. Code § 1802
(a)
(2)An electronic surveillance authorized by this subsection [without a FISC warrarnt] may be conducted only in accordance with the Attorney General’s certification and the minimization procedures adopted by him. The Attorney General shall assess compliance with such procedures and shall report such assessments to the House Permanent Select Committee on Intelligence and the Senate Select Committee on Intelligence under the provisions of section 1808(a) of this title.
In other words, not only does it require a (written) certification by the AG, but must be reported to the House and Senate Select Committees on Intelligence. According to statements from the House Chairman, that did not happen.
So it isn't required only suggested by the law. :)