Language based on RuleML and inspired by LKIF. Very good expressiveness and very poor tractability. Current state of the art for actual reasoning seems to be converting to modal defeasible logic and using SPINdle (Enabling Reasoning with LegalRuleML)
OASIS project, with participation from Governatori, Palmirani, Paschke… Seems to have the most momentum currently (2022) in terms of declarative legal semantics.
DR-CONTRACT: Governatori's earlier work doing contract stuff in straight RuleML. Similar ideas