The church houses today preach legalism a lot, and sometimes don't even know it. Sometimes it can be even as subtle as changing church house to "the church". Why is this important? Because it sets you up for the less subtle legalism. Like thanking everything from the pulpit is from God (we hope that it is), regardless of what God reveals about the subject, or the Written Word of God (the evil spirit quotes the Bible too).
We accept only what we were taught or born into believing. Then we wear our gang colors with pride, (Attitude: I'm a Baptist and I'm going to die a Baptist!) regardless of how that may drive some away from the gospel. This is sad because they are not being offended at the Cross at that point, just our institutionalized religion.
Once the evil spirit has you in a subtle form of legalism then he tries to get you deeper into it. Then he can teach the bible to you, any way he can, so as to disrupt your spirit flow. Like some who are reading this may have been falsely taught that legalism is only when one goes back and tries to get into Heaven by fulfilling the law of the Old Testament. That is just a form of it.
God would go further and say legalism is also making anything in Paul's letters as "law" no matter how inspired by God they are. They were never written to be a new law.