"Only US Citizens who are able to move to the Los Angeles area are eligible."

Not smart to advertise a job for US citizens only. You can't discriminate a broader class of people for employment even for national security positions.

Here is the actual statement from your company's website:

  This position must meet Export Control compliance requirements, therefore a "U.S. Person" as defined by 22 C.F.R. § 120.15 is required. "U.S. Person" includes U.S. Citizen, lawful permanent resident, refugee, or asylee.