When is a judicial development too late?

A simply-defined statutory offence may require detailed judicial development. Pending such development and final determination by the highest court the law may be unascertained and inaccessible.

Lower courts may develop the definition of an offence, and intermediate appellate courts may confirm that development, so that the law appears to be settled, and settled for some time, but suddenly the superior appellate court says no, everyone was wrong, here is what the ingredients of the offence really are.

In R v McRae, 2013 SCC 68 (6 December 2013) four judges – the trial judge and three appeal judges – had their definition of an offence overturned by seven judges of the Supreme Court.
The prosecutor had been able to appeal against the acquittal on a question of law: s 676(1)(a) of the Criminal Code. The Supreme Court ordered a retrial.

The defendant had been tried on five counts of uttering threats, an offence pursuant to s 264.1(1)(a) of the Criminal Code. This offence had been considered earlier this year but the Supreme Court then did not need to address the points raised in McRae: see R. v. O'Brien, 2013 SCC 2 (CanLII), 2013 SCC 2, [2013] 1 S.C.R. 7, mentioned briefly here on 31 January 2013.

The details of the definition of the offence as they were judicially elaborated need not detain us. The question I raise is, should the Supreme Court have ordered a retrial? There is no doubt that the power to make such an order existed. There could have been little objection (subject to the inaccessibility of unascertained law point mentioned above) to the first appeal court ordering a retrial. But given that the first appeal court was also wrong about the law, wasn't the law much more inaccessible and unascertainable than is acceptable? Shouldn't the defendant have been allowed his acquittals?

Compare the discussions of accessibility and ascertainability here on 13 March 2006, here on 9 May 2013, and here on 16 June 2013.