Can my husband drop my car off his auto insurance without me signing any documents because he is the sole owner of the policy?

If your husband is listed as the primary owner under the auto insurance policy where your car is listed as being an additional insured vehicle under it, he legally can do so. However, from a marital standpoint as well as a loss prevention issue, he should not have taken your car off his insurance policy without advising you of his intent and without you signing any documents.

I suggest that you and your husband have a sit down conversation tonight about this issue and why he did what he did without your apparent knowledge.

In short, yes.  It may be a community asset, but under his control, so he can do what he wants.  If this is a unilateral move on his part, then your marriage may have bigger problems.  Talk with an experienced family law attorney in your area to discuss your rights and options.