Ulpianus, On the Lex Julia et Papia, Book VI. We only understand those to be absent on public business who are absent not for their own convenience, but from necessity.

Ulpianus, On the Lex Julia et Papia, Book VI. I am of the opinion that he is absent in the service of the State whom the Emperor, as a special favor, has permitted to act as assessor in his own province; but if he does not so act by his permission, we must hold that, by doing so, he is guilty of an offence, and is not entitled to the privileges of those who are absent in the service of the State. 1A party is considered to be absent in the service of the State, as long as he fills some office, but as soon as his term of office is ended, he ceases to be absent on public business. We, however, calculate the time allowed him for his return from the date when he ceased to be absent in the public service, that is to say, as much as he requires to return to the City, and it will be reasonable to grant him the time which the law allows to other returning officials. Wherefore, if he turns aside on account of some affair of his own; there is no doubt that the time so consumed will not be granted him, but will be calculated with reference to the period within which he could have returned; and when this has elapsed we must say that he has ceased to be absent in the service of the State. It is evident that if he is prevented from continuing his journey by illness, humane considerations must prevail; just as is customary in case of bad weather, difficulties of navigation, and other things which accidentally happen.

Ulpianus, On the Lex Julia et Papia, Book VI. Where a Senator is permitted to marry a freedwoman by the consent of the Emperor, she will be his lawful wife.