The phrase "is surety for" is commonly used in legal and financial contexts to refer to a person or party who guarantees the fulfillment of an obligation or the payment of a debt. Antonyms for this phrase might include "does not vouch for," "disavows responsibility for," "disaffirms," or "renounces guaranty." These terms imply a lack of commitment, support, or willingness to assume liability for someone else's actions or financial obligations. When choosing a surety, it's important to consider their reputation, credibility, and financial stability, as well as any potential conflicts of interest or legal liabilities that could undermine their ability to fulfill their obligations.