They claimed they are the "dept. of legal affairs US treasury" in the voicemail message. When I call back, goes straight to voicemail each and every time. Is it a scam?

Yes, they are a scam.  There is no such thing as the Dept of legal affairs, US treasury. They probably want you to send them money by Western Union, which of course can't be traced.

First, they left the following message…

"This message is intended for "my first and last name". This is Adam Walker with the Department of legal affairs and I was trying to reach you in regards to a very important (mispronounced) issue. This is a verbal (mispronounced) notification for you in regards to the enforcement actions which have been started against your name. My number is 209-565-6371. I repeat that is 209-565-6371. If for any reason or to visit (?) a call back. I would suggest you to have your reading attorney to do it for you. As for (?) calling us, my (?) through a legal mess for you. I hope you would take this right and call me back. This is Adam Walker with the Department off legal affairs. Looking forward to speak to you, until then have a blessed day and goodbye."

Later the same day they called again (same caller id number), and I answered.  He barely speaks english.  Said something about an officer would be at my door in the morning to deliver a subpoena and proceded to verify my address.  Instead of my verifying my address, I started questioning him.  What was this in regards, and asked if he was the Federal Government… Yes, then he became more threatening.  I asked where are you calling from… California.  I said that an employee of the Federal Government would have better english… he became more enraged, and said something more about officers, subpoena, and then "have a blessed day".  I then said that an employee of the Federal Government would not say "have a blessed day".  He then said "You Mother F..ker!" and hung up.  

Called threatening legal action. Claimed his name was John Dorsey. I think he had a strong Indian accent. Department of legal affairs, US treasury, blah blah blah.  I wish there was someone in California I could call to report them.

Same msg as above....very broken English!  They hung up in desperation!  Also left msg prior to me answering call.