To Answer the Question:
In Islam all throughout history there have been many different opinions on Islamic Jurisprudence. Within Sunni School of thought there are 4 major Jurisprudence schools; Hanafi, Sha'fi, Maliki, Hanbali. In the Shia(Twelver) School of Thought there is only 1 school of jurisprudence known as Ja'fri.
These are the 5 Madhabs of Islam.
Now it depends on what you follow, if one of the school of thought says something is Halaal(and you follow that madhab).. then for you it is Halaal. You will not get a sin for that, because at first you tried to search for the truth and in your search you found that one of these madhabs is the most correct and then you aligned yourself with that madhab... Allah is the guider and if he guided you to that madhab... then your job is over..
This brings us to the discussion of Taqleed. Taqleed is a concept of Islam... where you search for the most knowledgeable Scholar and if you find someone you think has lots of knowledge of contemporary issues and he is able to Give Fatwas according Qur'an and Hadith in the light of contemporary issues. Then it is your job to follow him, do his Taqleed (Follow the Fatwas he gives)...
Now the question is what if the madhab I follow and Scholar I do taqleed of... what if something they say is wrong and in actuality haraam. In that case there will be no Sin upon you. Because your job was to find where Truth is... and if You Sincerely tried to search for the truth, with an open heart and found that particular madhab, scholar, etc... Then Allah is the guider and you will have no Sin upon you. Allah is also Most Merciful and Forgiving.