I was born into Catholicism. There is no papal decree excommunicating me there.
"Extra ecclesiam nulla salus", meaning, there is not much fun to be had in criticizing anything else but the papacy. This is the most important rule of the Holy Apostolic Church. As long as you keep criticizing, well within the statutes of limitation, you shall be deemed a member.
However, since there is no religious law to be kept in Christianity, it is a bit too lawless to my taste.
Yes, I know, Jesus still loves you.
Therefore, for all practical purposes, I consider myself to be a keeper of Islamic Law.
We need a law, and we have to find it somewhere. So, why not appropriate an existing, functioning system?
There is a lot of overlap, but in case of doubt, since the Christian view has no legal status, as far as I am concerned, it is the Islamic view that prevails.
Seriously, I am not a fan of lawlessness.