The specific part I don't understand reads
"The bodies of those who are condemned to death should not be refused their relatives; and the Divine Augustus, in the Tenth Book on his life, said that this rule had been observed. At present, the bodies of those who have been punished are only buried when this has been requested and permission granted; and sometimes it is not permitted, especially where persons have been convicted of high treason. Even the bodies of those who have been sentenced to be burned can be claimed, in order that their bones and ashes, after having been collected, may be buried."
source: https://droitromain.univ-grenoble-alpes.fr/Anglica/D48_Scott.htm#XXIV
The trouble for me lies in the way this is worded. At one point the author seems to explicitly state that under no circumstances should burial be denied to those condemned to death mentioning no exception. The author then goes on to explain "at the present time" there is exception, permission must be granted before burial is allowed. Is the author stating the rule and then showing that "presently" it is not being followed (because bodies are being denied)? Or is the author just mentioning a further aspect of this rule, being that bodies should never be denied to relatives provided that they have permission from the state?
Here's the Latin:
Corpora eorum qui capite damnantur cognatis ipsorum neganda non sunt: et id se observasse etiam divus augustus libro decimo de vita sua scribit. hodie autem eorum, in quos animadvertitur, corpora non aliter sepeliuntur, quam si fuerit petitum et permissum, et nonnumquam non permittitur, maxime maiestatis causa damnatorum. eorum quoque corpora, qui exurendi damnantur, peti possunt, scilicet ut ossa et cineres collecta sepulturae tradi possint.
The important part is this:
et id se observasse etiam divus augustus libro decimo de vita sua scribit. hodie autem eorum
That's this part in your translation:
and the Divine Augustus, in the Tenth Book on his life, said that this rule had been observed. At present, the bodies of those...
"At present" in Latin is "hodie autem" - "hodie" is "now" or "today;" "autem" is "but, on the contrary, on the other hand" or something along those lines. It's a strong break from what came before.
It looks clear to me that Ulpian is providing the example of Augustus as authority for the practice of returning the body, and noting that in current practice Augustus' example isn't always respected.