Okay, you asked for an outside source, it doesn't get any better than one of the rules authors for 3.5 since these rules are taken verbatim from 3.5. Here's what I found here
Spell Completion: This is the activation method for scrolls. A scroll is a spell that is mostly finished. The item user must complete the spell's verbal and somatic components (if it has any), but does not need any material, focus, or XP components the spell might have. (The character who scribed the scroll provided those.)
To use a spell completion item safely, you must be of high enough level in the right class to cast the spell already. If you can't already cast the spell, there's a chance you'll make a mistake, as noted on page 238 of the Dungeon Master's Guide. To activate a spell trigger item with an arcane spell on it, you must have levels in a class able to cast arcane spells. Likewise, to activate a spell trigger item with a divine spell on it, you must have levels in a class able to cast divine spells. If you don't have enough levels in the class to cast any spells yet, you can still try to use a spell trigger item, but your effective caster level for activating the spell is 0.
If a scroll has a caster level higher than your own, you have to make a Spellcraft check (DC = 1 + the scroll's caster level) to activate the scroll. If you fail the check, you don't activate the scroll and the scroll isn't used up
The entire section is on Spell Completion. Spell Trigger is discussed below that. The only oddity (which one could jump on if one wanted to dig in their heels) is that the author starts using the term Spell Trigger halfway through the paragraph. However, if you look at the entire context of the discussion, it looks like that's a mistake/Freudian slip. Why?
1. There's no transition into or out of nor any attempt contrast Spell Trigger with Completion in that paragraph or anywhere else during the Spell Completion
2. The author refers to Arcane and Divine items with Spell Triggers, but there is no such distinction with Spell Trigger.
3. In the actual Spell Trigger
section, he does not talk about Divine vs Arcane items, so again, I think it's reasonable to assume he's still talking about Spell Completion items throughout.
4. It wouldn't make any sense to talk about a Spell Trigger effective caster level being 0 as the spell on a Spell Trigger item is always that of the enchanting caster. It would make sense to talk about it for a Completion item because of the caster level check that is specifically required to use the scroll.
So, I read it like your previous mistake. You're thinking "1 minute" and you wrote "1 round." The important thing to note is that the use of the term "effective caster level is 0."
I'll compare this to the Kusarigama. While the boards say the weapon is not a Finesse weapon, if you read the weapon description, it seems plausible to allow it. Technically, caster level is not a requirement to use a scroll. The 3.5 archive suggests that if a caster level is needed, it's effectively zero. So it's reasonable to conclude that the rules authors are in fact saying that not having a caster level is tantamount to a caster level of zero. It's like saying you have don't have any oranges = 0 oranges if one needs to use your condition in a formula.