While there is "probably no legal obstacle" to prevent UK financial regulators monitoring foreign banks, Scotland could not force them to do so, solicitors from law firm Brodies have said.
Even a temporary exclusion from the European Union "would make doing business with other member states more complicated", Brodies' partner Elena Fry and public law associate Charles Livingstone also said.
It is "unlikely" that the EU would "happily agree to an opt-out" of the euro currency for Scotland, the solicitors said in the Christmas issue of insurance business periodical Post.
"The Scottish government is insisting that an independent Scotland would be an automatic member of the EU, on the UK's existing terms, regardless of the views of other member states," they said.
"Unfortunately, there is no precedent to support that argument - it simply hasn't happened before.
"Without any obvious mechanism in place, it is difficult to see how the Scottish government could force the issue of its membership over any potential objections from ratified EU members.
"If those nations do not want Scotland to achieve or inherit membership on independence, it's hard to see how the Scottish government could force the issue."
They have urged the financial sector to watch out for a "Scottish Government plan B" for financial regulation, highlighting the difficulties with its current plan and pointing out its ability to create regulators under independence.
"The Scottish government has proposed that the Financial Services Authority (FSA), or its successor bodies, the Financial Conduct Authority and the Prudential Regulation Authority retain responsibility for financial regulation in Scotland.
"There is probably no legal obstacle that would absolutely prevent such an arrangement, although EU law might raise some difficult questions. But it is not something on which the Scottish government could insist.
"There would be no way to impose Scottish responsibilities on the FSA against the UK government's wishes, so political agreement would be required."
A Scottish Government spokeswoman said: "Our policy to maintain the Bank of England as Scotland's central bank after independence is part and parcel of maintaining the pound as Scotland's currency, as part of a formal monetary union.
"Under these proposals, it therefore follows that the Bank of England will discharge the same responsibilities for an independent Scotland as it will for the rest of the UK in relation to the stability of financial institutions.
"A sterling zone will provide businesses both in Scotland and the rest of the UK with the certainty and stability for trade, investment and growth.
"As the Bank of England takes on the role of regulator for UK financial services, a very sensible and long overdue position, retaining the pound will preserve the highly integrated UK financial services market.
"Scotland has been an integral part of the European Union for almost four decades, so an independent Scotland will continue in EU membership. As many legal and constitutional experts have confirmed, Scotland is part of the territory of the European Union and the people of Scotland are citizens of the EU. There is no provision for either of these circumstances to change upon independence."