There is very much a constitutional requirement that the government can't tell you you can't have the lawyer you want because they are a US citizen. That's a clear violation of the 14th amendment right to due process...
A part of due process is the opportunity to be represented by counsel. Unless there are few or no quality lawyers who are not US citizens, I don't see how this would infringe on anyone's due process. Not being able to get the exact lawyer you want is not the same as your due process being violated.