Regulators monitoring dark pools
While MiFID II has introduced rules on trading volumes that may be transacted in dark pools. However, early signs suggest that the new regulations will result in trading migrating to systematic internalisers (SIs) a move. If this trend continues then the regulators have stated that they will rewrite the rules to take this into account.
https://www.ft.com/content/491bbfa8-f3ba-11e7-8715-e94187b3017e