Guards would regulate those who entered and departed.
( Guards ( ( would ( regulate ( those ( who ( ( entered and ) departed ) ) ) ) ) . ) )
(ROOT (S (NP (NNPS Guards)) (VP (MD would) (VP (VB regulate) (NP (NP (DT those)) (SBAR (WHNP (WP who)) (S (VP (VP (VBD entered)) (CC and) (VP (VBD departed)))))))) (. .)))
Guards checked who went in and out.
( Guards ( ( checked ( who ( went ( ( in and ) out ) ) ) ) . ) )
(ROOT (S (NP (NNPS Guards)) (VP (VBD checked) (SBAR (WHNP (WP who)) (S (VP (VBD went) (PRT (RP in) (CC and) (RP out)))))) (. .)))