WTO subsidy rules (agriculture aside) are specifically about not subsidising exports, and not causing "injury" to other countries (which is vague, undefined and therefore relies on dispute settlement).
#WTOisNotAHolyGrail
EU complaint against the US over subsidies for Boeing: wto.org/english/tratop…
US complaint against the EU over subsidies for Airbus: wto.org/english/tratop…