If your "partner" has a valid visa, then he has no problems with UCSICS. You failed to have an written agreement, so now you need to hire an attorney because your "partner" appears to know what he is doing and may very be getting legal advice.
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LLCs are unique business entities and the statutes governing their operation differ from state to state. This means that you're going to need an attorney licensed in MO and well versed in the Missouri Limited Liability Company Act and related case law in order to make a recommendation based on your specific circumstances.
That said, one member of an LLC typically cannot unilaterally terminate another member's ownership interest in the LLC unless they each signed a document (referred to as an "Operating Agreement," a "Company Agreement," or sometimes "Regulations" depending on your jurisdiction) that gave one member the ability to do so. Since you mentioned that no agreement was signed, in most states the gentleman you described in your fact pattern would probably have a difficult time successfully arguing that he had the authority to unilaterally terminate your husband's ownership in the LLC. That's the good news.
Now, from a practical standpoint - two member LLCs have a difficult time operating successfully under these circumstances. When there are only two owners, the LLC will have a difficult time making business decisions because there's no third party there to break the tie (assuming a 50/50 ownership). If the business has value (assets or a book of business), it is probably time to discuss splitting up the business and going your separate ways as amicably as possible. LLC member disputes often lead to litigation which can be expensive, time consuming, and sometimes destroy any value that might be left in the business.
Some other options include (1) offering to buy out the ownership interest of the other member and have your husband own the business by himself, (2) trying to sell the business to a third party, or (3) offering to sell your husband's interest in the LLC back to the LLC or the other member.
The main thing to remember in this situation is to remain cool-headed and get the right advice from a good business attorney in MO. He/she will be able to point you in the right direction. I wish you luck in resolving your difficult situation and recommend that you talk to an attorney ASAP.