MUN is a formal event therefore there is a strict dress code that has to be followed by every delegate. By principle, it falls under the category of “western business attire”, but what does this mean concretely?
For boys: a suit with a tie or bow are expected. Jackets are not required but are recommended. Therefore, jeans as well as shorts are not appropriate and won’t be accepted. The shoes should also be formal, so sneakers and sandals are not acceptable.
For girls: a nice blouse would be appropriate where no cleavage is visible. Once again, jackets are not required but are nice accessories. This should be combined with nice pants or skirts, as long as their length is under the knee. Formal shoes are required too, so sandals and flip-flops are not allowed. If a girl wishes to use a dress it should be a formal dress that would be appropriate for the event, not a cocktail dress and it would have to fulfill these requirements:
The dress may not be open below the middle of the back
Dress length must be no higher than the top of the knee
Concerning the tightness, it should be easy to gather an inch of fabric on either side of the dress anywhere except potentially at the waist