I would advise the OP not to pursue his former teacher unless they remained in contact and are already on a friendship level (at least). As someone who developed a huge crush on one of my married teachers, I think that the idea of a law restricting former students from dating their former teachers is ridiculous. Live and let live. Once you’ve passed the age of consent, there is no reason that their dating should not be allowed just because age differences make some people uncomfortable. However, it doesn’t sound like the OP actually had a deep/meaningful relationship with his former teacher (otherwise he would keep in touch with her and would have seen her in these past 3 years), so it’s probably just a fantasy that the OP wanted to live.