abortion is the moral equivalent of self defence. as a rational individual, you have bodily autonomy. nobody can force you to use your body for something you don't want it to be used for. and so no one can force you to use your body to carry a child. therefore, abortion is murder only if self-defence is murder. which it isn't. however, once there become viable options other than killing the fetus (e.g. birth through caesarian section), it becomes immoral to kill it.

absolute or constitutional? absolute -- hell no. constitutional -- a reasonable idea. some of the best countries (in terms of life expectancy, gdp per capita, political freedom) are constitutional monarchies. i'm thinking about UK, Netherlands, Norway, Sweden, Denmark, and Japan.