Basic tribal law, if a member of the tribe did it then it must be legal.
Today we learned according to the Barr memo that Barr's DOJ thought:
it isn't obstruction if you successfully obstruct an investigation such that investigators can't find evidence of a crime
it isn't obstruction if the people you instruct to do things as part of the obstruction don't do them
it isn't obstruction if you believe the underlying obstruction
it isn't obstruction if it would be hard to convict, and charging Trump for obstruction would mean any government official could be charged for obstruction. And also that lol we were kidding about 1), obstruction doesn't require an underlying crime.