Most of the petitions regarding immigration are submitted to the Nonimmigrant Bureau of Citizenship and Immigration Services. Some of the other petitions are also prepared for RIR. The applicant should furnish all the documents needed for the processing of the application. An immigration lawyer will guide you about the specificities. You can also gather information about the TN status. As for the Canadian professionals they can simply enter United States according to the rules of the new NAFTA. They need not file any petition with USCIS which is an absolute must for the H1 visa. In cases of any Canadian professional, they just have to appear before the USCIS inspector. The inspectors will only determine whether they are qualified to acquire a TN status. They should also have the necessary educational credentials and the professional degree for getting a TN visa. Most of the Canadians are known to have TN-1 status. You will not face any immigration problem regarding the TN status. However if you want to know about the legalities you can contact any of the good immigration lawyers from the Root Law Group. You can log on to http://www.rootlaw.com to know about the firm and its activities. They have a number of immigration attorneys who specialize in a number of fields.