Will my husband and I have trouble entering the U.S. as he is a Canadian citizen going to study at a US law school this fall, and I am a US Citizen?

Your Canadian husband may have a difficult time crossing the border if a CBP inspector discovers that he is married to a US citizen. That is of course because an F-1 student is supposed to have nonimmigrant intent, and that might be difficult to show in a situation where the spouse is a US citizen. I suggest that you maintain your student visa in Canada until your husband is able to enter the States as an F-1 student. The documentation that you have outlined for him to bring to the border is deficient in not listing proof of support, which is essential for F-1 students who are generally not allowed to work. If he decides to immigrate later and you will be sponsoring him for permanent residence, I suggest that you do not attempt to adjust his status to permanent residence here in the states as that might raise many questions with USCIS. A more roundabout but more acceptable route would probably be filing an I-130 petition, having it approved, and consular processing his immigration at the American consulate in Montréal. Due to the limitations of the Lawyers.com Forums, Alan Lee, Esq.'s (the "Firm") participation in responding to questions posted herein does not constitute legal advice, nor legal representation of the person or entity posting a question. No Attorney/Client relationship is or shall be construed to be created hereby. The information provided herein by the Firm is general, and requires that the poster obtain specific legal advice from an attorney. The poster shall not rely upon the information provided herein as legal advice nor as the basis for making any decisions of legal consequence.

Your husband will need an immigrant visa to come to the US, even to study, because he is presumed to have immigrant intent as a result of his marriage to you.  Intent to study is irrelevant since many permanent residents also intend to study.  If he doesn't want to remain a permanent resident after his studies are over, he can just abandon it by leaving the US permanently.