This is not much of a limitation. The Secretary is left with almost unbounded discretion to define what is an approvable program. Such unbounded discretion is the essence of the problem behind overbroad delegation claims. Courts will refuse to strike down statutes as overbroad if there is a history of practice that in effect narrows the agency's operative discretion. We have to check whether there is such a history here, but this seems unlike the banking cases of past carefully defined scope of regulation.
Courts also save broad delegations when specific procedures narrow agency discretion.
There are none here. Courts are especially sensitive to Constitutional claims, such as overbroad delegation, when there is a danger that the agency will harm important individual interests, such as First Amendment rights. There is no such danger here. But the agency's authority does relate to important federalism considerations. The agency has almost unbridled authority to dictate to the states what types of programs they must have if they are to get federal funding.