A losing case is just as important as a winning case because the court tells you what it would look for to rule in favor of a driver even though the subject driver lost.
The problem is the word "SHOULD". You need to understand a few words in standard speak:
SHALL is obligatory. If it says SHALL you don't have the option to do anything else.
SHOULD is a recommendation. It's a preferable way of doing it but isn't strictly required.
MAY is permissive. You're allowed to do that.
SHALL NOT is a prohibition.
Also, anything marked as "non-normative" is purely explanatory and not part of the standard proper.
As I said, I'd still make your case that the standard does recommend a better placement for the sign. However, it doesn't "require" it.
"No provision of this Act for which official traffic-control devices are required shall be enforced against an alleged violator if at the time and place of the alleged violation an official device is not in proper position and sufficiently legible to be seen by an ordinarily observant person."
This is SHALL NOT language which means it is a prohibition on enforcement of an alleged violation under the condition that proper position is not compliantly observed.
What is proper position? Proper position is determined by the MUTCD and any corresponding state amendments. In this case there are no state amendments. The MUTCD reads:
If No Left Turn (R3-2) signs (see Figure 2B-4) are used, at least one should be placed over the roadway, at the far left-hand corner of the intersection, on a median, or in conjunction with the STOP sign or YIELD sign located on the near right-hand corner.
So we have a SHALL NOT that precedes a SHOULD BE.
Yet, the SHALL NOT statute requires proper position. So for purposes of statutory construction it appears that the SHOULD BE language is tantamount to SHALL BE in the absence of any other statutorily authoritative determinant for proper position. Meaning since proper position is the standard by which the statute holds an alleged violator accountable, until and unless there is another standard for proper position the MUTCD is the only standard. Consequently, when the MUTCD says "SHOULD" there is no greater standard to appeal to that would establish proper position and is effectively a "SHALL BE".
Using the above, is there another reading of the statute that is more convincing?
The statute is independent of the MUTCD.
The statute says that you need proper placement (yes that is obligatory).
The question is if the placement is proper. The MUTCD recommends a given placement. You have to argue that's pretty convincing evidence of what is required, but I just want to point out that the MUTCD doesn't say you are obliged to place it that way, since it only says SHOULD not SHALL. However, you can argue that following the recommendations is a best practice for "proper" placement.
The issue here is that there is a statute which establishes obligatory standards via an external source and that external source then establishes standards that are less than obligatory. This is not internally consistent.
In order to establish consistency and comply with the intent behind the controlling statute which requires an obligatory proper position, then the MUTCD must be treated as obligatory as dictated by statute.
In summary, it appears while the MUTCD is not obligatory, the statute is, and there is no other standard by which proper position is defined so the MUTCD is de facto obligatory.
If a law, adoption, etc. is in "Substantial compliance" with the wording, etc., it is up to a court to determine if the facts governing the variance exculpates the defendant.
As an example, in Ohio police issuing a citation NOT in a distinctively marked car and not in a distinctive UNIFORM under the Evidence rules is incompetent to be a witness against the person he issued it to. Challenges were made that when the officer was NOT wearing his hat he was not wearing a distinctive uniform. The rulings were, paraphrasing, "The slight variance of an officer not wearing a hat, is not enough to throw out the ER, as the officer was in "Substantial compliance" with the ER.
You will find the SC doctrine in court rulings in every state I would imagine.
RJR said it. Even if the law specifically mandated conformance with the MUTCD, the placement statement you're referring to is not obligatory. What you're imagining is a statement that any "recommendation" in the MUTCD should somehow be obligatory, and then the law doesn't work that way.
You take your MUTCD recommendation and argue that it shows the lack of "proper placement" and leave out your baseless quibbling.
Here are a few examples:
Here are 2 cases my law dictionary cites under Substantial Performance [Compliance].
272 S.W. 616, 619
247 So. 2nd 72, 75
Here is a case discussing "Strict compliance" vs. "Substantial compliance".