No, spouses are not required by law to sign a personal guarantee: spouses are separate persons legally. A guarantee is perfectly legal and enforceable without a spouse's signature, and in fact, the vast majority of guarantees are *not* signed by spouses (unless those spouses are themselves part of the deal in some way, and so were required to sign by the company advancing the loan or providing the services, which required the spouses to sign as a condition of entering into the transaction).