In case anyone is curious, Canseco played in the MLB from 1985 to 2001. It is unclear when the MLB banned steroids, but some possible years include 1990--1991, 1997, or somewhere around 2003--2005.

Note, however, that steroid use was made effectively illegal on a federal level in the United States in 1990. The 1991 date above references a memo from the commissioner that states that illegal drugs are "strictly prohibited". Steroids are mentioned explicitly, though they do not have to be, seeing as how they were in fact illegal.

You can read the memo here: https://www.espn.com/espn/eticket/format/memos20051109