The phrase "are conditional upon" can be replaced by several synonyms to convey a similar meaning. "Dependent on" implies that something is reliant on a certain condition being met. "Contingent upon" suggests that a certain outcome or circumstance must be present for something else to happen. "Subject to" conveys that something is subordinate to certain conditions or limitations. "Hinged on" implies that something is based entirely on a specific factor or condition. "Pivotal to" suggests that something is of central importance and cannot exist without a certain condition being fulfilled. Ultimately, these synonyms all serve the purpose of indicating that something cannot occur without a specific condition being met.