Generally, not. There can be a problem if a foreigner is named and that person cannot be located. But a person can generally name whoever they wish to receive their estate/trust.
Depending on the nature of the assets in question, there could be income or other taxes associated with the assets, particularly if they are qualified assets such as IRAs, 401ks, 403bs or tax deferred annuities.
Your boyfriend should meet with an estate planning attorney to discuss the options available to accomplish his objectives. The attorney can be sure this is set up properly to minimize complications and tax consequences.
*** LEGAL DISCLAIMER I am licensed to practice law in the State of Michigan and have offices in Wayne and Ingham Counties. My practice is focused in the areas of estate planning and probate administration. I am ethically required to state that the above answer does not create an attorney/client relationship. These responses should be considered general legal education and are intended to provide general information about the question asked. Frequently, the question does not include important facts that, if known, could significantly change the answer. Information provided on this site should not be used as a substitute for competent legal advice from a licensed attorney that practices in your state. The law changes frequently and varies from state to state. If I refer to your state's laws, you should not rely on what I say; I just did a quick Internet search and found something that looked relevant that I hoped you would find helpful. You should verify and confirm any information provided with an attorney licensed in your state.
I concur with Mr. Frederick that this should not be a problem.
The above is general legal and business analysis. It is not "legal advice" but analysis, and different lawyers may analyse this matter differently, especially if there are additional facts not reflected in the question. I am not your attorney until retained by a written retainer agreement signed by both of us. I am only licensed in California. See also avvo.com terms and conditions item 9, incorporated as if it was reprinted here.
Attorney Frederick is correct. California law does not impose any requirement that a beneficiary of a trust or a will be a U.S. citizen or a spouse. See Prob C § 6102.
Citizen-spouses do receive special estate tax benefits, which non-citizen spouses do not receive. If you do get married in the future, you might want to consider speaking with an estate planning attorney or financial adviser to discuss options to maximize tax benefits.
I would also add that if the intention is to transfer property via a trust, make sure that the trust owns (or will own) the asset. A trust can only control property that it owns. Far too often, we see trusts that are unfunded and do not achieve the intended goals.
In addition to transfers via trust, there are other ways to transfer assets outside of probate, such as a 'pay on death' account, etc... An estate planning attorney may be able to assist in setting up a plan to achieve your boyfriend's intended goals.
DISCLAIMER: This response to your legal question on AVVO is general in nature and not intended to be, nor should it be considered specific legal advice to you. The information provided is based on general legal principals and is solely for educational purposes only. No attorney-client relationship is created between us by this response. You should consult with an attorney to whom you have provided all the facts of your situation and who can provide specific legal advice.