can someone who was illegal in U.S (2007) go back to U.S. after becoming a Canadian citizen? No criminal records whatsoever.

Thank you for your question.  This is a common scenario and one that we have addressed many times with clients from all over Canada. Depending on your prior immigration violations, you still may need a non-immigrant waiver to enter the U.S.  If you triggered an unlawful presence bar, or have some other type of immigration violation (ordered removed etc.), you will likely still need a non-immigrant waiver to enter the U.S. For a variety of different reasons, many foreign nationals find themselves inadmissible to the U.S. Inadmissible individuals cannot even enter the U.S. for a short shopping trip or even in-transit to another destination. Fortunately, however, most inadmissible foreign nationals can overcome their inadmissibility in order to enter the U.S. on a temporary basis by applying for a nonimmigrant waiver pursuant to section 212(d)(3) of the Immigration and Nationality Act ("INA"). Your should consult with an experienced immigration attorney who handles border and waiver matters for Canadian citizens.  The attorney should advise on non-immigrant waiver eligibility, parole options etc. Regards, Andrew M. Wilson, Esq. Serotte Reich Wilson, LLP www.srwlawyers.com awilson@srwlawyers.com