The European Parliament's power depends on which area of the EU it is working in. The EU has three areas, the "Community", its representation to other countries, and things to do with police and courts. In the last two areas, it can not do much as the Council takes care of those issues, but in the Community (which is the largest area) it can change or stop any law. But the Council also has to agree, and sometimes they disagree and cannot make a law.