because it was authorized by the court (with bad info)...... But Barr knows that..so there must be something else he sees
Surveillance done on the basis of an entirely legitimate FISA warrant (with its proper predicate) would be legal surveillance. However, there are many reasons to believe FISA warrants in this case were in no way legitimate. Further investigation will likely settle that portion of the matter. Without the proper predicate and "Woods procedure" evidence (pretty much known to be a slam-dunk NO! these people have shown themselves to be involved in a partisan coup to take out the opposition's standard bearer in a "novel" way not provided by the Constitution.
Under color of authority, top government officials uses the extremely powerful levers of government to punish and remove the opposition. It's almost certainly a set of capital crimes, punishable by death.