UN Security Council Resolution 1718 of 2006 says that:
(a) All Member States shall prevent the direct or indirect supply, sale or transfer to the DPRK, through their territories or by their nationals, or using their flag vessels or aircraft, and whether or not originating in their territories, of: (i) Any battle tanks, armoured combat vehicles, large calibre artillery systems, combat aircraft, attack helicopters, warships, missiles or missile systems
8 (b) The DPRK shall cease the export of all items covered in subparagraphs (a) (i)
Resolution 1874 in 2009 then extended that specific list of prohibited weapon systems to all kinds of weapons and weapon-related services as well:
- that the measures in paragraph 8 (b) of resolution 1718 (2006) shall also apply to all arms and related materiel, as well as to financial transactions, technical training, advice, services or assistance related to the provision, manufacture, maintenance or use of such arms or materiel;
So no, other UN member states would be in breach of that UN security council resolution if they would buy any weapon from North Korea.
However, as the answer by Severus Snape points out, what's legal and what's happening in reality are two different issues, especially when the customers are not internationally recognized governments.
And then there is of course the question if all those weapon systems the DPRK likes to parade around are actually as impressive as they look. Most public data about the capabilities of these weapons is provided by the North-Korean government media, which is known to heavily exaggerate the prowess of the DPRK. I am no weapons expert, but I am pretty certain that most countries should be able to procure far better gear from less politically controversial sources (except of course for those who are under international arms embargoes themselves).