Two US Supreme Court Justices to Give Rare Testimony to Congress. Really!

What is this all about? Was this necessary? Could this be a violation of the separation of powers?

Caveat: I am not familiar with the details of this event.

"While two Supreme Court justices are scheduled to field questions from a House panel Tuesday about the court’s budget, it’s plausible, if not likely, that members will use the opportunity to press the justices about some highly contentious cases.

Justices Amy Coney Barrett and Elena Kagan will appear before members of the House Appropriations Subcommittee on Financial Services and General Government. Some of the subcommittee members have been outspoken about recent high court rulings. ..."

Supreme Court Justices to Give Rare Testimony to Congress

Justices Amy Coney Barrett and Elena Kagan