I read those chapters a while back so I might not remember all the details but jace was clearly drugged on both occasions (second time I think the duke got him drunk on purpose and was intrigued by him at that point) and he more or less pleaded the duke to do him and the duke had plenty of occasions to quit the scenario. He was sober and he could have taken control of the scenario. He is also much stronger than jace so it would have been easy for him and it would have been more logical for him to brush jace off who was inebriated. The author could have written those scenes better but given that the duke is the "seme" here - he was simply written to take the lead instead of leaving jace alone. I would give that jace behaved inappropriately but he did not exactly assault the duke. It would seem like the duke more or less took advantage of him - more so during their second time together. Someone seemed to similarly confirm above how the events played out in the story. If I have missed any details or something that confirms otherwise then I hope someone could point it out.
y'all out here bad mouthing my mans blake but jace sexually assaulted blake too when they first had seggs. any form of forced/noncon sexual interaction can be considered as rape too.
there's no excuse to their actions but let's give them a chance ig ┑( ̄Д  ̄)┍