The thing is, the reason they gave her for banning in the initial letter they sent her is actually consistent with international law -- she was raising funds to send out a search and rescue ship which returns refugees to Libya.
The reason they gave was fundraising for a ship that was blocking SAR ships taking refugees to Italy. They included footage of her actions blocking such a ship in the past, together with her actual fundraising appeal in which she referred to stopping boats.
Not sure if it's against international law when conducted in international waters, but that's definitely against Patreon's content policy of fundraising for activities that endanger human life.