By popular acclaim—well, because three people on Twitter asked me to—I will now explain for you the first rule of enumerated clauses.
I’d like to say that the first rule of enumerated clauses was recovered from one of the cuneiform tablets that constitute the Kültepe texts, found in Kanesh, an archaeological site in Kayseri Province, Turkey. But in fact, I just made it up. Here it is:
If two enumerated clauses are separated by and or or, the first enumerated clause must be preceded by introductory text.
The introductory text could range from a single word (for example, if) to an independent clause (for example, Acme may terminate this agreement by giving notice to Widgetco if any of the following occur).
The aberration the first rule seeks to preclude is that on display in this extract:
This example displays a feature that in my experience is always present when the first rule is violated: subsection enumeration immediately followed by enumerated-clause enumeration (in this case, (a)(i)). When that happens, either the first enumerated clause is in fact not an enumerated clause but instead is just a confusingly structured subsection, or the enumerated clauses violate the first rule.
In this case, the first rule is violated because clauses (i) and (ii) are separated by and.
What’s wrong with violating the first rule? The first problem is that you’re setting the reader up for a miscue. A reader would likely assume they’re about to read a unit that’s equivalent to a section, but when they encounter the next enumeration, they’ll realize that their semantic framing was mistaken, and they’ll do a double-take.
The second problem is that violating the first rule is either pointless or sets you up to violate the second rule of enumerated clauses. In this case, the enumerated clauses are pointless: it would have been better to present the two enumerated clauses as separate sentences, without an and.
If instead the enumeration designates actual enumerated clauses, with text following, that’s where you violate the second rule of enumerated clauses:
End each set of enumerated clauses with a period, instead of adding text that builds on the enumerated clauses.
For an example of text that violated the second rule, see this September 2020 blog post.
But that’s enough for now, except note that I use the word rule. We’re not talking about the laws of thermodynamics here. Instead, we’re dealing with how to handle enumerated clauses sensibly, acutely aware that people will regularly screw things up.