Here is the law, you be the judge for yourself:

Polygamy was against the law in Illinois. An Illinois state law was enacted February 12, 1833:

• "Bigamy consists in the having of two wives or two husbands at one and the same time, knowing that the former husband or wife is still alive. If any person or persons within the State, being married, or who shall hereafter marry, do at any time marry any person or persons, the former husband or wife being alive, the person so offended shall, on conviction thereof, be punished by a fine, not exceeding two years." (Revised Laws of Illinois, Vandalia: Greiner & Sherman, 1833, pg. 198-199).

Shortly prior to Joseph Smith's death in Carthage, he was charged with the crime of polygamy. See:

History of the Church, vol. 6, pg. 405 (May 25, 1844)

• "Saturday, 25 -- At home, keeping out of the way of expected writs from Carthage. Towards evening, Edward Hunter and William Marks, of the grand jury returned from Carthage; also Marshal John P. Greene and Almon W. Babbitt, who informed me there were two indictments found against me, one charging me false swearing on the testimony of Joseph H. Jackson and Robert D. Foster, and one charging me of polygamy, or something else, on the testimony of William Law, that I told him so! The particulars of which I shall learn hearafter. There was much false swearing before the grand jury."

To learn more about Joseph Smith's practice and denial of polygamy at the same time visit:
http://www.mindspring.com/~engineer_my_dna/mormon/denpract.htm

To learn more about Joseph Smith's polgyamous relationships with married women visit:
http://www.mindspring.com/~engineer_my_dna/mormon/menwives.htm

Sincerely,

James