The problem with treating human embryos as property

A woman in the UK has lost her final appeal to be given the chance to implant embryos which were created by her and her ex-fiancee. Her ex-fiancee wants the embryos destroyed.

After the decision, Ms Evans said: "I am distraught at the court's decision. It is very hard for me to accept the embryos will be destroyed."

The UK's law treats IVF embryos as the shared property of both individuals up until the point of implantation. But what if (and why doesn't) UK law treated human embryos created by sexual intercourse the same way? Would a man, who had unprotected sex with a woman, be able to demand every measure be taken to prevent the woman's uterus from accepting the implantation of a human embryo which could have resulted from the couple's sexual intercourse?

How can a change in location ( in a lab vs. traveling down a woman's fallopian tube) change what a human embryo is or isn't?