Can anyone who can trace descent from the noble families of old valyria go inside the black wall of volantis? Like if a targaryen, velaryon or rogare visits volantis would they automatically gain entrance, or would they still need an invitation?

Here’s how it works:

“…the Black Wall that had been raised by the Valyrians when Volantis was no more than an outpost of their empire: a great oval of fused stone two hundred feet high and so thick that six four-horse chariots could race around its top abreast, as they did each year to celebrate the founding of the city. Outlanders, foreigners, and freedmen were not allowed inside the Black Wall save at the invitation of those who dwelt within, scions of the Old Blood who could trace their ancestry back to Valyria itself.” (ADWD)

Emphasis mine. Even if you’re of the blood of Old Valyria, if you weren’t born within the Black Walls of Volantis, you need an invitation.