Myers v. United States and presidential acquiescence

On Thursday I wrote about the exchange over signing statements in Zivotofsky. Among other things, oral argument included the following:

CHIEF JUSTICE ROBERTS: So we should give no weight to the fact that the Chief Executive signed the law that he is now saying has such a dramatic - that his successor, but I gather the position is the same - is now saying has such deleterious effects on American foreign policy? Well, as a general matter, does that have any consequence at all?

GENERAL VERRILLI: No. I mean, I think this Court held - I think this Court held in Myers that the fact that one President signed a law into - signed a law that violated separation of powers doesn't have any effect.

For reasons that Chief Justice John Roberts elaborated (and I discussed Thursday), there might be specific reasons that the president's decision to sign a law with an unconstitutional provision does demonstrate something about the gravity of the unconstitutional provision. But here the solicitor general is invoking a more general proposition.

Josh Blackman asks about the source of this general proposition:

I think the Solicitor General is referring to Myers v. United States-the removal case-but that case is not cited anywhere in the government's brief. I'm afraid I don't know where it says that in Myers. What law was signed in Myers? It involved the removal of an officer? I've read the case a number of times, but can't recall. If you know, please add a citation to the comments.

I think it's this passage, from page 170 of Chief Justice William Howard Taft's opinion in Myers:

In spite of the foregoing Presidential declarations, it is contended that, since the passage of the Tenure of Office Act, there has been general acquiescence by the Executive in the power of Congress to forbid the President alone to remove executive officers - an acquiescence which has changed any formerly accepted constitutional construction to the contrary. Instances are cited of the signed approval by President Grant and other Presidents of legislation in derogation of such construction. We think these are all to be explained not by acquiescence therein, but by reason of the otherwise valuable effect of the legislation approved. Such is doubtless the explanation of the executive approval of the Act of 1876, which we are considering, for it was an appropriation act on which the section here in question was imposed as a rider.

So that's the source of the general principle that the solicitor general refers to, for what it's worth.