Edinburgh Law School professor Drew Scott said that there had been a change in attitudes in Brussels since the Scottish referendum in 2014.
And he dismissed previous suggestions that Spain could veto EU membership for an independent Scotland because of its stance on Catalonia.
Speaking at a fringe event on Europe at the SNP conference in Aberdeen, professor Scott said: "The mood in Brussels today is quite different from the mood in Brussels in 2014 before the independence referendum.
"I don't see this as a political point, it just is a fact of life that there is now a much higher degree of recognition that Scotland is a mainstream European country where 62% voted to remain, and I suspect although it's not been tested that would now be higher given what people see what the leave options are, that Scotland would take its place relatively quickly, relatively comfortably within the European family of nations and would continue to contribute as it has done.
"We don't make enough in this country, and I mean Scotland now, of the contributions that we've actually added to the European project."
Professor Scott continued: "I think Scotland could take its place relatively comfortably, relatively quickly providing we're prepared to accept the obligations of membership and assuming we had achieved independence by a constitutional due process.
"The Spanish shadow is always raised but I think Spain's position is quite clear, I think it always has been quite clear actually, that if Scotland becomes independent under a constitutional process which is accepted by all parts of the UK and all citizens of the UK, then Spain's got no particular problem with that because it's a quite different situation from that which exists within Spain.
"So I don't see the shadow of a Spanish veto at all lying over this."