When is it possible to carry out the "En Passant" manoeuvre? This manoeuvre is a form of pawn capturing technique. When a player’s pawn jumps two spaces on a first move, that piece can then be taken from the side as the opposing pawn moves into the moving pawn’s “lane” behind it, capturing it.

My question is, are there any other conditions where this move cannot be carried out such as to prevent check or checkmate or to carry out a check or checkmate?

Also, is this move allowed in tournaments and the like?
You can't take a pawn en passant if that pawn just made a discovered check to your King:

8/8/7k/8/2p5/8/3P4/2B1K3 w - - 0 1

1. d4+


After 1. d4+ Black is in check (their king is attacked by the White bishop on c1) so he has to move his King. 1...cxd3 is not allowed.

Also, it can't be carried out if your pawn is pinned to your king:

6k1/8/8/8/2p5/8/B2P4/4K3 w - - 0 1

1. d4


The Black pawn on c4 is pinned by the White Bishop on a2. If that Pawn moves, the White Bishop would be able to take the Black King. So after 1. d4 the move 1...cxd3 is not allowed.

I can't think of any other condition where this move can not be carried out.

And yes, en passant is allowed in tournaments of course. But when you take a pawn en passant, do not say "en passant" aloud (some low rated players do that, they also say "check" aloud when they put the other player's king in check) since it can break your opponent's concentration (and the concentration of the other players near you in the playing hall).

Wikipedia has a good article on the en passant rule.