When is a citation unnecessary because the conclusion is obvious?

Slavery was abolished → enslaved people were no longer legally slaves.

That is essentially a definitional consequence.

The meaning of “abolition of slavery” already entails the disappearance of the legal status of slavery.

Similarly:

A person jumps from a roof and the person may be injured.

That is not quite as purely definitional because injury is probabilistic, but suppose you actually establish:

The person fell from the roof and broke his leg.

Then:

The person was injured.

requires no scholarly citation merely to establish the elementary logical consequence.

But consider:

Slavery was abolished and capitalist labor markets expanded.

Now we have moved beyond the definition of abolition.

Why?

Because abolition tells us about legal status. It does not, by definition, tell us what happened to labor markets.

That requires historical evidence or reasoning about consequences.

So my proposed rule is quite useful:

The farther a conclusion moves beyond what is contained directly in the meaning of the original fact or statement, the greater the need for evidence or explicit reasoning.