The Russian government is mulling it over (or pretending to):
“The WTO gives us some additional possibilities,” Ulyukayev was quoted by Interfax as saying on Wednesday. “We at the WTO council in Geneva talked about the possibility of filing lawsuits against the U.S. over the sanctions against Russian banks and we hope to use the mechanism of the WTO to keep our partners in check regarding this issue.”
I know little about this topic so I emailed a colleague who had this to say (I edit slightly):
There is the purely doctrinal question whether the sanctions can be interpreted to contravene some GATS banking commitment by the US respecting market access or non-discrimination. Even if yes, and I do not know the answer, there is still Art. XIV bis on national security exceptions that applies for measures to protect “essential security interests” in “war or other emergency in international relations.” That arguably applies although there is no case law. Add that a WTO case would take three years, by which time all of this is presumably old news anyway.
The broader question of to what extent sanctions can be used under WTO law has received some attention, but is of dubious practical significance. We have embargoed Cuba (a GATT member) for 50 years. No one worried much about GATT during apartheid in South Africa, either.