I know someone who vented their portable aircon into their (fully vented) bathroom. the build up of heat and humidity melted their soap and had tiles falling off the wall.
If there is any doubt about existing by-laws forbidding this, get one drawn up and adopted at an EGM.
However, I reckon a Notice To Comply with any by-law regarding damage to common property and or allowing fumes on to common property (if you have one) would be a good starting point.