It was through private email to ticket holders. It came in yesterday (bolding mine).
*This email is sent to those who purchased tickets for Olympic Games Tokyo 2020 at the lottery phase.
*To prevent this message from being classified as spam, this email does not contain the URL of the Tokyo 2020 Official Ticket Website.
*English follows Japanese.
電話番号：0570 - 00 - 2020（有料・ナビダイヤル）
For those who purchased Tokyo 2020 Games ticket,
The decision was made at the Five-Party meeting held on 8 July that no spectators will be allowed into venues located in Tokyo, Kanagawa, Chiba and Saitama during the Olympic Games.
We deeply regret for all the ticket purchasers that this measure had to be put in place, though it is a critical measure to prevent the infection spread.
It was announced in the evening of 9 July, following the Five-Party meeting and the local government authorities meeting, that the sessions held at the venue in Hokkaido would have spectators. However, the government of Hokkaido has decided that spectators will not be allowed in the venue in Hokkaido to prevent people from Tokyo to visit Hokkaido, as the state of emergency has been declared in Tokyo. Therefore, sessions at the venue in Hokkaido will also be held with no spectators.
Tickets for the sessions being held without spectator or invalidated as a result of the lottery will be refunded. You do not need to apply for refund for such tickets. We will send an email about the details of the refund and method to your registered email address after the Games.
For the venues located in Miyagi, Fukushima, Ibaragi and Shizuoka, spectators up to 50% of venue capacity and not more than 10,000 people will be allowed. Some sessions are subject to the lottery to reduce spectators, the result of which has been announced in the early morning on Saturday, 10 July.