This topic can get confused. Here is why. Salvation is free,absolutely free,nothing can be added for the initial born again experience.
OK,now ALL RELIGIONS,require the adherant to DO in order to be "accepted" . It could be "legalism"
But the thing is,one could look at Peter's false doctrine of circumcision and say "legalism" and they would be right,and these are blatant extreme examples.
What about the more subtle ones?
What about us that are absolutely grace oriented and ooze grace from every pore,but gossip over someones trangression,or tell someone they did this or that while we are not aware that we run a stop sign or fudge a expense report,or eat a grape at the supermaket.
The point is,if I break one law,I might as well break 100 laws.
But legalism can also be performance oriented as opposed to one that is abiding in Him,waiting on Him,and following the Lamb.
Legalism in todays church,IMHO,is more subtle than blatant. We see the radical legalist,but we tolerate the subtleties of others AND OURSELVES.