QUESTION: I was a bit confused about what exactly makes the spending clause moot.
ANSWER: Just to make sure we are clear about the relevant question, let me make two points. First, I do not think the subsequent spending legislation rendered the original lawsuit about the DPPA moot. Second, the Spending Clause itself cannot be moot; the question is whether the appropriations legislation rendered the first lawsuit, challenging the coercive DPPA, moot.
QUESTION: Is it because the enumerated powers under the commerce clause make the regulation constitutional, so then the other question about other constitutional problems becomes moot?
ANSWER: No, that is a different question -- whether the government's success in the first lawsuit would render a challenge to the appropriations legislation moot. And the answer to that question (which we did not address in class) would have to be yes. If the states must comply with the DPPA regardless, then conditioning their highway dollars on compliance with that law (which they must comply with no matter what) is no longer an issue. In class, though, we were discussing a different question -- namely, did the enactment of the appropriations legislation render the lawsuit challenging the DPPA moot. And the answer is no. South Carolina might well have decided to decline the 25% of its highway funding at stake under the appropriations legislation. And if it did so, it would need to know whether it must comply with the DPPA regardless. In all events, South Carolina needed to know whether the coercive DPPA was constitutional to make an informed choice as to whether to accept the highway dollars under the appropriations legislation. Thus, there remained a live controversy. South Carolina was still "injured" to the extent it was being forced (or imminently forced) by federal law to do something that it wished not to do.