akhi, no, seriously, I do understand your point, BUT we as muslims can never judge or defend people by laws other then the shariah, I'll try to explain my point in short:
you know tawheed?
the three categories of tawheed stand for
-tawhid in Ibada (worship) uhulliya
-tawhid in ruling, don't know the english word but I mean tawheed ar rububiya
-and tawhid in names and 'personalities' (again I don't know the right english word, but i mean asmaa wa sifaat.)
You need to have all three to complete tawheed, and without a full tawheed, your actions are not worth anything.
surah muhamad,8-9
But those who disbelieve (in the Oneness of Allâh Islâmic Monotheism), for them is destruction, and (Allâh) will make their deeds vain.
That is because they hate that which Allâh has sent down (this Qur'ân and Islâmic laws, etc.), so He has made their deeds fruitless.
look: surah an nisa, 65: But no, by your Lord, they can have no Faith, until they make you (O Muhammad SAW) judge in all disputes between them, and find in themselves no resistance against your decisions, and accept (them) with full submission.
The mushrikeen, can believe in 2 of the tawheed categories, but lack 1, so their tawheed is not correct, this is the same when you are ruling, or supporting to rule according to other laws then the sharia, wich you are doing when you are a lawyer for western laws. In this case you are lacking tawhide ar rububiya.
listen: az-zuchruf 87-88. And if you ask them who created them, they will surely say: "Allâh". How then are they turned away (from the worship of Allâh, Who created them)?
Allâh has knowledge) of (Prophet Muhammad's) saying: "O my Lord! Verily, these are a people who believe not!"
And I didn't even mention the things you sometimes have to defend, like homo's, murderers, just kufaar. And I can asure you, that as a lawyer they won't let you wear your islamic clothing, beard, hijaab.
And a muslim in the american congress, that doesn't exist either he is in the american congress or he is not a muslim!
28. Let not the believers take the disbelievers as Auliyâ (supporters, helpers, etc.) instead of the believers, and whoever does that will never be helped by Allâh in any way, except if you indeed fear a danger from them. And Allâh warns you against Himself (His Punishment), and to Allâh is the final return.