Mr. Perl's translation of the Japanese is close, although it would better be stated (still a literal translation): "Because it is dangerous, entering is forbidden." (Abunai kara, haitte wa ikemasen)

In Japanese, a subject can be (and usually is) implied rather than stated, and the implied subject can change several times in the course of a single sentence, without any explicit verbal signal that any change has occurred.

Fascinating language; much more supple than English. I've always felt that successfully speaking Japanese is somewhat akin to mind-reading.