It wasn't illegal (unconstitutional) at the time they did it, which is different from not knowing. They would have had to see the future to know.
Also keep in mind "illegal" and "unconstitutional" are different levels - "illegal" deals with specific laws, "unconstitutional" deals with violating a person's rights. Laws can be declared unconstitutional and repealed.
Also keep in mind "illegal" and "unconstitutional" are different levels - "illegal" deals with specific laws, "unconstitutional" deals with violating a person's rights. Laws can be declared unconstitutional and repealed.