Here I'll raise one tangential point. The Administration says it's not bound by earmarks contained only in legislative history, and (in a fact sheet) cites the following language from Cherokee Nation v. Leavitt (2005):
where Congress merely appropriates lump-sum amounts without statutorily restricting what can be done with those funds, a clear inference arises that it does not intend to impose legally binding restrictions, and indicia in committee reports and other legislative history as to how the funds should or are expected to be spent do not establish any legal requirements on the agency . . . .(quoting Lincoln v. Vigil (1993), and in turn other cases). It's worth asking why the Court is uniformly hostile to legislative history in interpreting appropriations measures when the Justices remain divided over the relevance, if any, of legislative history in interpreting other statutes. For instance, even in Cherokee Nation itself, on a slightly different point, Justice Scalia wrote a separate concurrence restating his longstanding view that committee reports are just about always irrelevant to statutory interpretation. But he was the only Justice to make this point.
Let me suggest my solution to the puzzle: There isn't in fact a different rule regarding the relevance of legislative history for appropriations measures and other statutes; it's just that even those Justices who care about legislative history in general accept that it only comes into play where the statutory text is ambiguous; and where a statute's text makes a lump-sum grant to an agency, that pretty unambiguously confers on the agency the discretion to spend the money as it sees fit (consistent with other legal restrictions). But, I would venture that if the terms of an appropriation really were ambiguous, then the Justices who reject the Scalia view of legislative history in general would be willing to look to an earmark contained in a committee report for evidence of what Congress intended in the appropriation.
Posted by Mike Dorf