Catalysis of the reaction: L-pipecolate + acceptor = delta1-piperideine-6-carboxylate + reduced acceptor. Delta1-piperideine-6-carboxylate is also known as 2,3,4,5-tetrahydropyridine-2-carboxylate.
L-pipecolate:(acceptor) 1,6-oxidoreductase activity