If a person guarantees a conditional obligation, the person's liability is commensurate with that of the principal and the person is not entitled to notice of the default of the principal unless the person is unable, by the exercise of reasonable diligence, to acquire information of the default and the creditor has actual notice of the default.
Liability Upon Guaranty Of Conditional Obligation -- Notice Of Default
Mont. Code Ann. § 28-11-206, under Guaranty -- Liability and Exoneration of Guarantor.
Mont. Code Ann. § 28-11-206