Beginner rules question

Hi All,

A question about the basic chess rules:

When analysing one of my games, the system does not let me capture the white bishop with the black king in this position. I thought that since the knight is pinned and it is illegal for it to move, it cannot possibly still be counting towards the bishop's protection? So I thought that it would be legal to make the capture here. Am I wrong, or is this a system bug?

Thanks.

The Black king cannot capture the White bishop.  It is illegal to move your king into check (the knight would be attacking the king).

You can also think about it this way:  If the Black king took the bishop, White would be able to take the Black king before the rook could take the White king.  Therefore, the knight is still protecting the bishop even though it is pinned to the White king.

Thanks.