UN arms embargo on Iran was meant to expire on Sunday, October 18, but in August the US activated “snapback sanctions,” a mechanism in the 2015 Iran deal that would cancel its “sunset clauses” lifting various sanctions on the Islamic Republic. In other words, the US made sure the arms embargo would not expire – and no other country countered that move during the month in which that was possible.
Since the US left the Joint Comprehensive Plan of Action, as the deal is known, in 2018, the other parties to the agreement say the US does not have the authority to reinstate sanctions, and they will view the embargo as lifted on Sunday. However, the US argues that sanctions and the snapback are part of UN Security Council Resolution 2331, which lists the US specifically as a party, and not just the JCPOA.
All of this is to say that next week there could be a showdown between Russia and China, which want to sell Iran weapons, and the US, which has been using its economic might to enforce sanctions on the regime for the past two years and announced further measures last month.