Have the feds been enforcing anything in states that have not made marijuana legal? It seems that maybe only state level and below authorities are enforcing the

Have the feds been enforcing anything in states that have not made marijuana legal? It seems that maybe only state level and below authorities are enforcing them. There are sometimes cases where laws that go unenforced for a long time can eventually become unenforceable. I wonder if this could happen federally to normal marijuana possession. The legal principle is called desuetude.