Off the top of my head, everything in the US and countries with strong labor/environmental laws gets a US certified "cruelty free" sticker with little checkboxes under it that state that no child labor, etc. was used. No one else gets to have a label unless they pay to have their entire supply chain certified on a yearly basis.

The absence of a label will be taken as the product did in fact use child labor, unsafe work environments, etc. just like the lack of an organic label is taken to mean that the farm uses pesticides when in fact, it could just be they couldn't afford certification.

You make a good point. Much "organic" produce in the US is now grown in China, particularly of processed ingredients. China is selling the certification, the food is grown in toxic soil with fertilizer and pesticide, then a gentleman signs off that it is organic and it can be sold in foreign markets for a premium to naive customers.

Certifying that something is "child labor free" or "slavery free" is just as reliable.

Especially in a factory, you shouldn't trust anyone giving you numbers that are too good to be true. Sure, you can have automated processes that keep track of things, but if anything unexpected happens (which is common) and the processes change in ways the monitors don't expect, your numbers become meaningless.