Sentence:  To him , law <WSD>is</WSD> the command of the sovereign ( the English monarch ) who personifies the power of the nation , while sovereignty is the power to make law - i. e. , to prevail over internal groups and to be free from the commands of other sovereigns in other nations . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)