They were, yes. Louisiana may have joined the Southern rebellion but that doesn't mean that they, or any other Southern state, were ever out of the Union.
There was no rebellion. Louisiana seceded, Louisiana didn't "rebel" because a) Louisiana was, and is, sovereign, and b) Louisiana made their own decisions to join, and to leave, the Union. People don't "rebel" against the People. Ergo, there was no rebellion.
Louisiana's decision was taken a pay grade above the Union and the Constitution -- it was taken at the People level. Only God gets over that.