Cite your reference to Federal Labor Law (provide link). I'd like to read where the federal government sees a voluntary termination as involuntary. The VSP was no disguise. It was voluntary. Yes some states still paid out unemployment, but not all. The company stated that they would not contest any unemployment claims. I had some friends who took the VSP who got benefits and others who didn't, depending on their state.
From Benefits.gov
Who is eligible for Unemployment Insurance?
To be eligible for this benefit program, you must meet all of the following:
>>Unemployed through no fault of your own, and>States may have specific requirements determined by state law.<<