At the moment, individuals could only rely on publisher reputation. Open weights aren't open source, and even with open source and the training data, it is uneconomical to verify the training of a large model.

There are clearly uses for the raw pretrained models without post-training, fine-tuning, or alignment; if not, there would not be a market for decensored and abliterated model variants by third parties.

If reputable model publishers could instead publish their models in verifiable parts: pretrained weights, fine-tuning/alignment adapters, and a combined intended-use model - this would reduce the attractiveness of malicious fine-tune publishers. I'm not holding my breath for that though, quite the opposite. I expect the economic and power incentives will encourage the big training players to push for ever-higher but nebulous safety regulations until everyone else is choked out except for them.

Until training costs come down, and perhaps even after that, all AI should be treated as untrusted rogue agents, constrained by default regardless of source. That's just the sensible thing to do, but the economics will have something to say about that.