Maybe the AMF had information about accounts in USA and tipped the SEC?
[0] https://lautorite.qc.ca/en/general-public/media-centre/news/...
EDIT:
More information: The court order preventing him to launch Plexcoin was issued on July 20[1]. He did not comply and was charged for court contempt in September. The court found him guilty on oct 17 2017[2].
[1] https://lautorite.qc.ca/en/general-public/media-centre/news/...
[2] French only - https://lautorite.qc.ca/grand-public/salle-de-presse/actuali...
If you trade GBP/USD and then USD/EUR then you have to abide by SEC regulations.
If you sell PLEX/USD then you have to abide.
So anyone offering PLEX/USD has to comply with the freeze.
And if they have any accounts in dollars that will be frozen.