Sentence:  But they [police juries] have no power to [...] issue promissory notes or <WSD>warrants</WSD> to cover funds which may be set aside for this purpose in future taxation without express authority from the supreme political power of the state. 
Meaning of the word marked with <WSD> tags:  An option, usually issued together with another security and with a term at issue greater than a year, to buy other securities of the issuer.