When he bought a dog his mother had begun the life of the law.这个正确吗

When he bought a dog his mother had begun the life of the law.
这个正确吗

When he bought a dog,his mother had begun the life of the law.
当他买了一条狗的时候,他妈妈开始了法律的生活.
语法是对的,但意思没看懂