Is it legal for a Bar to not serve you alcohol if your of legal age?

is it legal for a Bar in Scotland to refuse a paying customer alcohol if they're of legal age and not caused trouble or anything?

I don't see how that is legal, you best just find another pub, but to answer your question I don't see it to be legal as the customer should be able to buy wares if the seller is selling. Try the bar again, if that doesn't work out then there really isn't any point going to court over purchase of alcohol :P Best find another pub.

Hopefully this helps!

Some jurisdictions require bartenders and waitresses to refuse service to anybody they consider intoxicated. Other jurisdictions don't allow them to refuse service based on race, religion, gender etc. The missing information here is the reason they gave for the refusal.