Can a project be licensed as "open source", yet place a restriction on who can utilize the software?
For example, if my software falls under software export controls, can I continue to license it as "open"?
From the Open Source Definition:
The license must not discriminate against any person or group of persons.
The license must not restrict anyone from making use of the program in a specific field of endeavor. For example, it may not restrict the program from being used in a business, or from being used for genetic research.
So a license restricting who can use your software isn't open source.
About the question regarding export restrictions: yes you can license it as OSS, even if it falls under export restrictions. Your license allow the usage, but laws might restrict it. That doesn't mean your license isn't open source.
Yes and no.
Referring to Mnementh's answer, the official definition of open source dictates that you can't, because you can't discriminate (laws excepted: export restrictions don't count).
However, it all depends how strict you want to be with your open-source licensing. You could quite easily license your project in the spirit rather than the letter of open source: making the source code available, making it easy to use and reuse, etc.
tl;dr: Technically no, but yes if you're flexible.