The following is CBP’s response to the American Immigration Lawyer Association's liaison question on concurrent employment under TN visa status.
AILA Question: Can an individual in TN-1 status obtain another concurrent full time (or part time) TN-1 position with another employer?
CBP Reply: Concurrent TNs – yes. Part-time employment only is acceptable.
From AILA-CBP Liaison Meeting, AILA Doc. No. 08060450 (April 18, 2008).